Date: August 14, 2004
by Chaya Venkat
Since CLL is a disease of the immune system, it makes intuitive sense that as the CLL gets entrenched, more and more functions of the immune system are corrupted. One of the areas where this dysfunction can become serious is the inability to tell the difference between "self" and "non- elf". It is a little bit like having a police force that is no longer able to distinguish between criminals and solid citizens, letting the bad guys roam free and shooting dead perfectly law abiding citizens.
Autoimmune disease happens when a confused and corrupted immune system starts attacking perfectly good cells, something that should not happen under normal conditions. While there are many forms of autoimmune disease, we will limit ourselves to AIHA (autoimmune hemolytic anemia) in this article. Roughly 11% of CLL patients with advanced disease will develop full blown AIHA, but as many as 30% of CLL patients may be at risk for developing it. In simple terms, their immune systems start attacking red blood cells, and if these crucial oxygen carriers are killed off faster than they can be replaced by the bone marrow, the result is anemia, low hemoglobin levels and low hematocrit. Anemia is a quality of life issue. Low red blood cell counts and low hemoglobin lead to poor oxygen supply to the tissues, which in turn lead to fatigue. Left untreated, deep and persistent anemia can be life threatening.
Semin Oncol. 1998 Feb;25(1):80-97.
Autoimmune disease and chronic lymphocytic leukemia: autoimmune hemolytic anemia, pure red cell aplasia, and autoimmune thrombocytopenia.
Diehl LF, Ketchum LH.
Department of Medicine, Walter Reed Army Medical Center, Washington, DC
Immune dysregulation, a hallmark of chronic lymphocytic leukemia (CLL), manifests itself in three autoimmune diseases: warm autoimmune hemolytic anemia (AIHA); idiopathic thrombocytopenia (ITP); and, pure red cell aplasia (PRCA). AIHA occurs in 11% of advanced stage CLL patients. Prednisone is the first treatment of choice, with 90% responses and 65% complete responses. More than 60% of patients relapse when treatment is stopped. Intravenous immunoglobulin, the next line of treatment, causes responses in 40% of patients. While the data are very limited, cyclosporine A is a reasonable choice for third-line therapy. Alkylating agents, danazol, plasma exchange, immunoabsorption, vincristine-loaded platelets, splenectomy, and splenic irradiation are also reported to cause responses. The data on mechanisms of AIHA are most consistent with immune dysregulation leading to loss of tolerance to a self antigen which in turn leads to the immune-based hemolytic anemia. PRCA is underrecognized in CLL with 6% of CLL patients having PRCA when tested for it. Unlike AIHA, PRCA often occurs in early stage disease. Anemia, reticulocytopenia, and a marrow virtually devoid of red blood cell precursors are hallmarks of PRCA. Corticosteroid therapy is the first line of treatment. If a response is not obtained in 4 weeks, cyclosporine A should be added. Although the data on pathophysiology are very limited, PRCA appears to be the result of an abnormal T cell that both fails in its normal function to support growth and inhibits the growth of erythroid progenitor cells. ITP occurs in 2-3% of CLL patients, occurs in early stage disease and may be a presenting manifestation. Initial therapy for ITP mirrors the guidelines for primary ITP. Initial therapy should consist of prednisone. Seventy percent of patients respond. Splenectomy is a reasonable second- ine treatment. Autoimmune phenomena, largely related to blood cells, are based in the immune dysregulation of CLL. Longer survivals in CLL patients, more treatment regimens per patient, and more immunosuppression with modern treatments, allow us to predict an increasing incidence of autoimmune blood cell diseases in CLL.
Am J Hematol. 2002 Nov;71(3):177-83.
In vitro production of anti-RBC antibodies and cytokines in chronic lymphocytic leukemia.
Barcellini W, Montesano R, Clerici G, Zaninoni A, Imperiali FG, Calori R, Cortelezzi A, Zanella A.
Dipartimento di Ematologia, IRCCS Ospedale Maggiore di Milano, Via F. Sforza 35, 20122 Milan, Italy.
B-chronic lymphocytic leukemia (B-CLL) patients have a high prevalence of autoimmune phenomena, mainly autoimmune hemolytic anemia (AIHA). Immunoregulatory cytokines play a role in the regulation of both autoimmunity and leukemic B-cell growth. Mitogen-stimulated direct antiglobulin test (MS-DAT) is a recently described test able to disclose latent anti-RBC autoimmunity in AIHA. We investigated the prevalence of anti-RBC autoimmunity by MS-DAT and the pattern of cytokine production by PHA-stimulated whole blood cultures from 69 B-CLL patients and 53 controls. Results showed that anti-RBC IgG values in unstimulated, PHA-, PMA-, and PWM-stimulated cultures were significantly higher in B-CLL patients compared with controls. In B-CLL, the prevalence of anti-RBC autoimmunity was 28.9% by MS-DAT, compared with 4.3% by the standard DAT. Production of IFN-gamma, IL-2, IL-13, TNF-alpha, sCD23, and sCD30 was significantly increased in all B-CLL patients compared with controls, whereas there was no difference in IL-4, IL-6, IL-10, and TGF-beta production. Multivariate analysis showed that IL-4 was significantly increased in MS-DAT-positive compared with -negative patients. Patients with autoantibody positivity displayed greater IFN-gamma production than negative patients. These data are in line with the hypothesis that autoimmune phenomena in B-CLL are associated with an imbalance towards a Th- 2-like profile. The elevated prevalence of anti-RBC autoimmunity found by MS-DAT suggests that an underestimated latent autoimmunity exists in B-CLL.
Copyright 2002 Wiley-Liss, Inc.
New insights into the why and how of AIHA may help open up better therapy choices, so I will try to give you a quick peek into how your immune system works, how it can get corrupted, and what you can do to help yourself.
As in any military campaign, accurate intelligence is necessary to figure out exactly who the bad guys are, and poor intel makes for blunders on the battlefield. (Let's not go too far with this analogy in this election year. We don't want to get into a political debate on CLL Topics, do we?). "Military Intelligence" in the context of the immune system is proper presentation of tell-tale markers of the bad guys to the killers of the immune system. These markers are called "antigens", and they identify the cells marked for killing. Dendritic cells are the professional snitches that do this job very well: they are also called Antigen Presenting Cells (APCs). In a pinch B-cells can also present antigens. Below is a British paper hot off the presses, suggesting that part of the problem with AIHA is that screwy CLL cells get into the act by fingering innocent red blood cells, setting them up as targets for assassination. The killer are usually cytotoxic T-cells ("CTLs") which obediently take the word of the CLL cells, and kill the innocent red blood cells. Inaccurate intelligence provided by defective B-cells leads to the wrong guys getting killed, red blood cells in this case.
Blood. 2004 Jul 29 [Epub ahead of print]
Rh Autoantigen presentation to helper T cells in chronic lymphocytic leukemia by malignant B-cells.
Hall AM, Vickers MA, McLeod E, Barker RN.
Department of Medicine and Therapeutics, Institute of Medical Sciences, University of Aberdeen, Aberdeen, United Kingdom.
Chronic lymphocytic leukemia (CLL) is frequently associated with autoimmune diseases directed against constituents of the blood, including hemolytic anemia (AIHA). We hypothesized that CLL cells predispose to hematological autoimmunity by acting as aberrant antigen presenting cells (APC). Initially, it was confirmed that all studied patients with AIHA secondary to CLL harbored activated Th cells specific for epitopes on the dominant red blood cell (RBC) autoantigens in primary AIHA, the Rh proteins. Rh specific Th cells were also detected in a number of CLL patients who, although they did not suffer AIHA, had low levels of anti-RBC antibody in their serum. Fractionation of putative APC populations from the peripheral blood of patients by negative selection showed that CD5(+) CLL cells are the most effective cell type in processing and presenting purified Rh protein to autoreactive Th cells. This ability was confirmed using positively selected CD5(+) CLL cells. Thus, our study provides the first evidence for malignant cells driving an autoimmune response by acting as aberrant APC.
Antigen presenting is hardly the major function of B-cells. The thing they do best, the very reason for their existence, is the production of immunoglobulins, Ig for short. B-cells that have been exposed to antigens once can remember the bad guys for long periods of time. This memory function is very important, so that our bodies can quickly mount an effective defense against various pathogens and invaders. There is a huge amount of detail here, but for now let us simplify things, and look at broad brush strokes. B-cells produce three kinds of immunoglobulins, IgG, IgA and IgM, with slightly different functions - different guard duties so to speak. Some types of Ig is needed to protect the skin and tissue, some to protect the blood supply, some to guard against the entry of pathogens through the lining of your gut, lungs, mouth or other mucosal surfaces.
Here is the interesting bit: clonal CLL cells in most patients express IgM, and since they are all clones, all of them express the same IgM. But it is now pretty clear that AIHA is not caused directly because of the IgM made by CLL cells, but by IgG that is made by the remaining (non-clonal, or polyclonal) "good" B-cells. Strange, right? Well, the story is that IgG is capable of attacking not just external invaders and bad guys, it also reacts to some home grown targets, among them the targets on red blood cells. In healthy individuals, this tendency of the IgG to attack home-grown targets ("self antigens") is kept under control by IgM. Think of it as the seasoned and "Mature" IgM keeping tabs on the impetuous and "Gung-ho" IgG, which is otherwise prone to shoot first and ask questions later. Now it becomes clear - in CLL patients with very large number of cancerous B-cells, most of the IgM itself comes from the cancer cells and is incapable of restraining the attacks of the IgG on red blood cells. CLL-spawned IgM is not directly responsible for red blood cell killing, but it is indirectly responsible because it fails to do the job of controlling IgG made by good B-cells.
How do we use this information to our advantage? Well, for starters it explains why in most cases AIHA happens only when the tumor load is high. When there are only few good B-cells present and lots of the CLL cells, the good IgM is drowned out by the malfunctioning IgM produced by the CLL cells. If this ratio were different, in other words if there was more good IgM and less bad IgM, then once again we can hope to keep the gung-ho IgG under control. That is exactly what happens when AIHA patients are given intravenous infusions of immunoglobulins collected from the blood of healthy volunteers. At least for a while, there is enough good immunoglobulin to keep things under control, which in turn controls the killing of red blood cells, and therefore AIHA.
Obviously, another good way of changing the balance in favor of good IgM from good B-cells, versus the ineffective variety from CLL cells is to reduce the tumor load, reduce the number of CLL cells present and never let them get too numerous in the first place. In other words, any therapy that reduces CLL tumor load will prove to be of help in controlling the AIHA as well. In the past, corticosteroids such as prednisone were among the frontline drugs to control CLL, and therefore they were also among the first drugs used to control AIHA. Now, more modern drugs such as Rituxan may be used as frontline, not just to treat the CLL itself but by the process of reducing the amount of ineffective IgM in circulation, tilt the balance in favor of the effective IgM produced by good b-cells, which then keeps the lid on the dangerous activities of IgG.
Leuk Lymphoma. 2001 Jun;42(1-2):163-76.
Broad alterations of self-reactive antibody-repertoires of plasma IgM and IgG in B-cell chronic lymphocytic leukemia (B-CLL) and B-CLL related target-restricted autoimmunity.
Stahl D, Lacroix-Desmazes S, Sibrowski W, Kazatchkine MD, Kaveri SV
INSERM U430, Universite Pierre et Marie Curie, Hopital Broussais, Paris, France
B-cell chronic lymphocytic leukemia (B-CLL) is characterized by a malignant CD5+ B-cell clone. The leukemic clone commonly expresses IgM antibodies exhibiting reactivity toward a wide range of self-antigens. However, B-CLL associated autoimmunity is typically restricted to self-antigens expressed by blood cells, and mediated by IgG autoantibodies of polyclonal origin. In the present study, we addressed the question whether self- eactive antibody repertoires of plasma IgM and IgG are disturbed by monoclonal immunoglobulins of B-CLL patients, and whether antibody repertoires of patients exhibiting B-CLL associated target-restricted autoimmune disease (AID) differ from those of B-CLL patients without AID. We investigated antibody repertoires at a global level, using a technique of quantitative immunoblotting that allows for the quantitative screening of antibody reactivities in complex antibody mixtures toward a large panel of antigens derived from homologous tissue extracts, followed by multiparametric statistical analysis of the data. We demonstrate that self-reactive antibody repertoires of plasma IgM and IgG are broadly altered in patients with B-CLL, that alterations in self-reactive antibody repertoires are not restricted to B-CLL patients exhibiting AID, and that target- estricted autoimmunity in B-CLL patients is associated with altered antibody repertoires not restricted to the target organ. We conclude that monoclonal alterations of immunoglobulin production in B-CLL are associated with broad defects of self-reactive antibody repertoires. Our observations suggest that the application of therapeutic IVIg preparations might influence B-CLL by restoring normal self-reactive antibody repertoires in plasma.
Leukemia. 2002 Oct;16(10):2092-5.
Rituximab-based chemotherapy for steroid-refractory autoimmune hemolytic anemia of chronic lymphocytic leukemia.
Gupta N, Kavuru S, Patel D, Janson D, Driscoll N, Ahmed S, Rai KR.
Division of Hematology/Oncology, Department of Medicine, Long Island Jewish Medical Center, New Hyde Park, New York
Autoimmune hemolytic anemia (AIHA) is a well known complication of chronic lymphocytic leukemia (CLL). Steroids are the first line of treatment and there are limited effective treatment options for steroid refractory AIHA of CLL. Rituximab, an active agent against B cell malignancies, has also been noted to be active in certain autoimmune hematologic disorders. We used a combination of rituximab, cyclophosphamide and dexamethasone (RCD) in eight CLL patients with steroid refractory AIHA. Rituximab was given at a dose of 375 mg/m(2) i.v. on day 1 (D-1). Cyclophosphamide was given at a dose of 750 mg/m(2) on D-2. Twelve mg of dexamethasone was given i.v. on D-1, D-2 and orally from D-3 to D- . Cycles were repeated every 4 weeks till the best response. Response in AIHA was evaluated by frequent blood counts and Coombs test. All eight patients achieved a remission of their AIHA. Median pretreatment hemoglobin was 8.3 g/dl and post-treatment hemoglobin was 14.3 g/dl. Five patients converted to Coombs negative after RCD. Median duration of response was 13 months (7-23+). Retreatment with RCD was also effective in achieving a response on relapse of AIHA. Our results indicate that a rituximab-based combination regimen (RCD) is highly effective in treating steroid refractory AIHA of CLL.
Here then, is the good news: with more options and better understanding of the therapy possibilities for AIHA (and the other autoimmune diseases as well), autoimmune cytopenia is no longer the immediate and automatic kiss of death. AIHA and its more dangerous cousin ITP (autoimmune idiopathic thrombocytopenia, which is a long winded way of saying destruction of platelets by pretty much the same mechanisms as AIHA) used to be the among the defining characteristics of end-of-the-road late stage CLL. Not any more. Do read the article on Rai staging and what is wrong with it to get more of the details, Staging Does Not Predict Survival. As the abstract below points out, while 9 out of 10 patients respond to immunosuppressive therapy (prednisone, a corticosteroid, is a good example), if this is the method used to control the CLL and therefore the AIHA, there is risk of serious infection, as well as risk of secondary cancers that use the window of opportunity to gain a foothold. Sounds to me a safer way of controlling the AIHA is to use drugs such as Rituxan, safer for controlling the CLL and safer for controlling the AIHA. What do you think, what makes sense to you? Or are you a fan of long-term or high-dose steroid use?
Am J Hematol. 2003 Sep;74(1):1-8.
Autoimmune cytopenia does not predict poor prognosis in chronic lymphocytic leukemia/small lymphocytic lymphoma.
Kyasa MJ, Parrish RS, Schichman SA, Zent CS.
Division of Hematology/Oncology, Department of Medicine, Central Arkansas Veterans Healthcare System and University of Arkansas for Medical Sciences, Little Rock, Arkansas
Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is characterized by an acquired immune defect that can cause autoimmune complications, including anemia and thrombocytopenia. We conducted an observational study of the epidemiology, clinical presentation and significance of autoimmune complications of CLL/SLL in 132 patients from a large population (>45,000 veterans), in which at least 90% of patients with CLL/SLL have been previously identified. Over a period of 12.5 years, 12 patients (9.1%) had autoimmune complications; of these, 6 (4.5%) had autoimmune hemolytic anemia (AIHA), 5 (3.8%) had immune thrombocytopenia (ITP), and 1 (0.8%) had pure red blood cell aplasia (PRBA). All 6 cases of AIHA had a positive direct immunoglobulin test for IgG and C3d. In 6 patients, CLL/SLL was an incidental finding at the time of presentation with autoimmune cytopenia. Nine out of 10 patients responded to immunosuppressive therapy, which was complicated by serious infection in 7 cases, one of which was fatal. The major cause of mortality in patients with autoimmune complications of CLL/SLL was secondary malignancy. Survival of patients with immune cytopenia was not significantly different from CLL/SLL patients without immune cytopenia. Among patients with anemia or thrombocytopenia, mortality was significantly higher in those with bone marrow failure compared to an autoimmune etiology. We show that in a non-referred population with a high incidence of CLL/SLL, autoimmune cytopenia can occur early in the natural history of the disease. These data suggest that the Rai and Binet classifications for CLL need to be modified for patients with autoimmune cytopenia.
OK, if you are with me thus far: AIHA can be controlled by using intravenous immunoglobulin infusions to tilt the balance in favor of good Ig versus cancer-corrupted Ig, or using drugs such as Rituxan to control the root cause CLL. Let us look at some other ways of controlling the CLL that might be considered. Fludarabine is not something you want to do, if you have AIHA. In fact, it is prudent to get yourself tested for incipient signs of autoimmune problems (Coombs test, also called DAT or direct antiglobulin test) before you indulge in fludarabine therapy. There is now a credible level of information that says fludarabine therapy may make the autoimmune problems worse. It is now clear that fludarabine therapy is not very selective: it kills the CLL cells alright, but in the process it mucks up the efficient working of the other arms of the immune system. This makes it all the more easy for cytotoxic T-cells (CTLs) to get on with the job of exterminating red blood cells. Moral of the story, if you have AIHA, it would be smarter to stay away from fludarabine therapy.
Hematol Cell Ther. 1998 Jun;40(3):113-8.
Severe autoimmune hemolytic anemia in eight patients treated with fludarabine.
Gonzalez H, Leblond V, Azar N, Sutton L, Gabarre J, Binet JL, Vernant JP, Dighiero G.
Service d'Hematologie, Hopital Pitie-Salpetriere, Paris, France.
We have used fludarabine to treat 36 patients with various lymphoid malignancies, including 29 with chronic lymphocytic leukemia (CLL). All these patients were heavily pretreated, and FAMP was prescribed on a compassionate basis. Eight patients (22%) developed severe autoimmune hemolytic anemia (AIHA) during or after treatment, and one died. Five patients had no previous history of hemolysis. These cases confirm the high incidence of AIHA after FAMP and suggest that the use of highly effective lymphocytotoxic agents such as fludarabine in heavily pretreated patients increases the risk of AIHA in CLL and other lymphoproliferative disorders.
If you tell me this section is heavy on the jargon, I will agree with you. But I urge you to take the time to read and understand this part. There are some really neat action items that pop out of this logic, nifty things you can discuss with your doctor. Such as: have you ever heard of treating AIHA with garden variety anti-viral medications? I knew I would get your attention with that!
Let's get into it. We discussed in a previous article, Neupogen as Booster to Rituxan Therapy, how Rituxan works. Rituxan, too, is an IgG, it just happens to be a man-made IgG, created to target only CD20 as its sole antigen target. We described how it is a "Y" shaped molecule and the arms of the "Y" are pincers shaped just right for grabbing on to CD20. Well, the "natural" IgG in your body is also a "Y" shaped molecule, and some of these molecules have pincers shaped just right for harmless markers on red blood cells. In a healthy person, these "self reactive" IgG's are controlled and neutralized by the proper functioning of IgM. Not so in patients with CLL and AIHA. Without effective IgM control, the self reactive IgG attaches itself to the antigen markers on red blood cells. That is the start of the problem.
As in the case with Rituxan tagging CD20 on CLL cells, this tagging of the red blood cell by IgG is not by itself always enough to kill the targeted cell. An additional element is often required - killer cells (also called effector cells) such as neutrophils, macrophages, NK cells are needed to deliver the death blow. We described how the tails of the "Y" shaped IgG molecule latched on to their target cell are irresistibly attractive to the killer cells. This is especially so if the killers are activated into a frenzy, activated to grow the right receptors to attach themselves to the IgG tails. These receptors are called FCgammaReceptors. So the scenario is this: innocent red blood cell, tagged by self reactive and uncontrolled IgG by means of the pincers at the tips of the "Y" shape of the IgG, and now the tail of the "Y" attracts the killers to home in and finish the job. In fact, if you can somehow see to it that FCgammaR is not expressed by the effector cells, AIHA is significantly controlled. In the abstract below, mice specially bred not to have FCgammaR were protected from AIHA, whereas control mice were not.
Blood. 1998 Dec 1;92(11):3997-4002.
FcgammaRIII (CD16)-deficient mice show IgG isotype-dependent protection to experimental autoimmune hemolytic anemia.
Meyer D, Schiller C, Westermann J, Izui S, Hazenbos WL, Verbeek JS, Schmidt RE, Gessner JE.
Departments of Clinical Immunology and Functional Anatomy, Hannover Medical School, Hannover, Germany.
In autoimmune hemolytic anemia (AIHA), there is accumulating evidence for an involvement of FcgammaR expressed by phagocytic effector cells, but demonstration of a causal relationship between individual FcgammaRs and IgG isotypes for disease development is lacking. Although the relevance of IgG isotypes to human AIHA is limited, we could show a clear IgG isotype dependency in murine AIHA using pathogenic IgG1 (105- H) and IgG2a (34-3C) autoreactive anti-red blood cell antibodies in mice defective for FcgammaRIII, and comparing the clinical outcome to those in wild-type mice. FcgammaRIII-deficient mice were completely resistent to the pathogenic effects of 105-2H monoclonal antibody, as shown by a lack of IgG1-mediated erythrophagocytosis in vitro and in vivo. In addition, the IgG2a response by 34-3C induced a less severe but persistent AIHA in FcgammaRIII knock-out mice, as documented by a decrease in hematocrit. Blocking studies indicated that the residual anemic phenotype induced by 34-3C in the absence of FcgammaRIII reflects an activation of FcgammaRI that is normally coexpressed with FcgammaRIII on macrophages. Together these results show that the pathogenesis of AIHA through IgG1-dependent erythrophagocytosis is exclusively mediated by FcgammaRIII and further suggest that FcgammaRI, in addition to FcgammaRIII, contributes to this autoimmune disease when other IgG isotypes such as IgG2a are involved.
We may ask which killers are the most effective in doing this foul deed? Which effector cells go on a killing rampage once the red blood cells are tagged by uncontrolled and self reactive IgG? Turns out macrophages from the spleen are the most determined killers. In fact, one of the ways (rather a drastic way, I am afraid) of controlling AIHA is to remove the spleen. No spleen, no spleen-dwelling macrophages to do the heavy duty killing of red blood cells.
Am J Hematol. 2004 Mar;75(3):134-8.
Laparoscopic splenectomy for autoimmune hemolytic anemia in patients with chronic lymphocytic leukemia: a case series and review of the literature.
Hill J, Walsh RM, McHam S, Brody F, Kalaycio M.
Department of Hematology and Medical Oncology, Cleveland Clinic Foundation, Cleveland, Ohio
The purpose of this study was to evaluate the safety and efficacy of laparoscopic splenectomy in patients with chronic lymphocytic leukemia (CLL) complicated by autoimmune hemolytic anemia. A series of nine such patients who underwent this procedure at our institution between August 1997 and September 2001 were retrospectively reviewed. Seven of 9 patients who underwent laparoscopic splenectomy for CLL and autoimmune hemolytic anemia achieved a complete response. One patient who initially responded relapsed 12 weeks postoperatively. Therefore, six of 9 patients showed sustained responses with a mean follow-up of 2 years, consistent with other published series. Two patients had no response, one of whom died within 3 weeks of surgery from transformed Hodgkin's disease. The only other postoperative complication occurred in a patient who developed pneumonia. We conclude that laparoscopic splenectomy is a safe and effective treatment for autoimmune hemolytic anemia in patients with CLL who fail medical therapy.
Copyright 2004 Wiley-Liss, Inc.
Is there an easier way of getting rid of splenic macrophages, short of eliminating the spleen? I don't know about you, but I sort of like to keep factory installed-equipment. Leaving behind a piece of yourself on the operating table is not a decision to be taken lightly. Below is an abstract that caught my eye. Macrophages are the garbage trucks of the immune system, they literally eat their enemies. In fact some large bacteria are best handled by macrophages, which literally surround the bacteria and engulf it. What happens if you have a particle that is the right size to attract the attention of macrophages, and this Trojan horse has in it a drug that kills the macrophage once it is engulfed? Good question. Turns out that a liposomal formulation of clodronate does exactly this. In case you have not heard of clodronate, it is a relatively harmless drug used to treat osteoporosity (brittle bones) brought about by calcium leaching out of the bones, often prescribed to menopausal women. Clodronate (and the later generation bisphosphonates such as Fosamax) are not the new technology here - the delivery mechanism of the drug encapsulated inside little lipid droplet (fat globule) to make them attractive to macrophages, that is the sexy part. These authors suggest that liposomal clodronate first blocked the macrophages and then killed them, within 24 hours. This caused a reduction in killing of red blood cells and the effect lasted 1-2 weeks in their animal studies. In other words, this is like a temporary and medicinal (as opposed to very permanent and surgical) splenectomy. I like both the bits - about it being temporary and non-surgical. If you want to learn more about liposomal clodronate, there is a whole website devoted to just that, here is the link: http://www.clodronateliposomes.org/. The cartoon picture below is from this website.
You can also read the full text of the abstract below by clicking on the link provided below. This is interesting research, and I would like to see it progress to clinical trials in real patients. Right now it is still in the lab, and the inventors are trying to make sure they have all their ducks in a row in terms of patent rights before going further.
Blood. 2003 Jan 15;101(2):594-601. Epub 2002 Aug 29.
Liposomal clodronate as a novel agent for treating autoimmune hemolytic anemia in a mouse model.
Jordan MB, van Rooijen N, Izui S, Kappler J, Marrack P.
Department of Immunology, and the Howard Hughes Medical Institute, National Jewish Medical and Research Center, Denver, CO
Autoimmune hemolytic anemia (AIHA) is a disease in which autoantibodies against red blood cells (RBCs) lead to their premature destruction. Most clinically significant autoantibodies are of the immunoglobulin G (IgG) type, which leads primarily to the uptake and destruction of RBCs by splenic and hepatic macrophages. Therapies such as corticosteroids and splenectomy are directed at interfering with this process. Liposomally encapsulated clodronate (dichloromethylene diphosphonate) has previously been found to be a potent antimacrophage agent. It selectively depletes animals of macrophages within 24 hours of administration by inducing apoptosis in these cells. Therefore, we hypothesized that liposomal clodronate would be a useful agent for treating AIHA. We tested this hypothesis in a mouse model of AIHA in which animals were given either anti- BC antibodies or preopsonized RBCs. In either case, liposomal clodronate substantially decreased RBC destruction. This drug formulation was effective within hours by first blocking and then depleting phagocytic macrophages, and its action lasted for 1 to 2 weeks. Thus, in AIHA, liposomal clodronate therapy may act like a temporary, medicinal splenectomy. As such, it may prove useful in situations where rapid response to therapy is critical or other medical therapies are inadequate.
So far so good, we have learned that one of the major mechanisms for AIHA involves macrophages on the rampage, which are attracted by the tails of the out-of-control IgG attached to innocent red blood cells. What gets the macrophages (and other effector cells) so hopping mad, up-regulating their FCgamma receptors and making them such mean killing machines? Our bodies are well tuned to respond to threat. Immune system cells are particularly good at going into a high state of alert, DEFCON 4 as it were, when they receive signals that suggest an attack is taking place and all good macrophages must go to their battle stations. A viral or bacterial infection could do the job. A viral infection that increases lactate dehydrogenase (LDH: you should be familiar with this term on your blood test reports) can send out the necessary danger signals, getting the macrophages all riled up and ready to kill any cell that is tagged by an IgG, tail flapping ever so attractively in the breeze. Does this suggest something to you? How about a nice course of appropriate anti-viral medication, get rid of the nasty virus, reduce the level of LDH, calm down the overly stimulated macrophages, slow down the killing of red blood cells? In other words, the viral infection by itself may have nothing to do with the killing of red blood cells, but by its very presence it can create danger signals of inflammation that drive macrophages into overdrive, exacerbating the AIHA. What is not to like? By the way, this logic seems to work not just for AIHA, but its more dangerous but less frequent sibling ITP. Below are two abstracts that say it is not such a crazy idea, this business of autoimmune disease precipitated by viral infections.
J Virol. 2000 Jul;74(13):6045-9.
Exacerbation of autoantibody-mediated hemolytic anemia by viral infection.
Meite M, Leonard S, Idrissi ME, Izui S, Masson PL, Coutelier JP.
Unit of Experimental Medicine, Christian de Duve Institute of Cellular Pathology, Universite Catholique de Louvain, Brussels, Belgium.
Strong enhancement of the pathogenicity of an antierythrocyte monoclonal antibody was observed after infection of mice with lactate dehydrogenase-elevating virus. While injection of the antierythrocyte antibody alone induced only moderate anemia, concomitant infection with this virus, which is harmless in most normal mice, led to a dramatic drop in the hematocrit and to death of infected animals. In vitro and in vivo analyses showed a dramatic increase in the ability of macrophages from infected mice to phagocytose antibody-coated erythrocytes. These results indicate that viruses can trigger the onset of autoimmune disease by enhancing the pathogenicity of autoantibodies. They may explain how unrelated viruses could be implicated in the etiology of autoantibody-mediated autoimmune diseases.
Blood. 2004 Jun 17 [Epub ahead of print]
Exacerbation of autoantibody-mediated thrombocytopenic purpura by infection with mouse viruses.
Musaji A, Cormont F, Thirion G, Cambiaso CL, Coutelier JP.
Unit of Experimental Medicine, Institute for Cellular Pathology,Universite catholique de Louvain, Brussels, Belgium.
Antigenic mimicry has been proposed as a major mechanism by which viruses could trigger the development of immune thrombocytopenic purpura (ITP). However, because antigenic mimicry implies epitope similarities between viral and self antigens, it is difficult to understand how widely different viruses can be involved by this sole mechanism in the pathogenesis of ITP. Here we report that in mice treated with anti-platelet antibodies at a dose insufficient to induce clinical disease by themselves, infection with lactate dehydrogenase-elevating virus (LDV) was followed by severe thrombocytopenia and by the appearance of petechiae similar to those observed in patients with ITP. A similar exacerbation of anti-platelet-mediated thrombocytopenia was induced by mouse hepatitis virus. This enhancement of anti-platelet antibody pathogenicity by LDV was not observed with F(ab')2 fragments, suggesting that phagocytosis was involved in platelet destruction. Treatment of mice with clodronate-containing liposomes and with total IgG indicated that platelets were cleared by macrophages. The increase of thrombocytopenia triggered by LDV after administration of anti-platelet antibodies was largely suppressed in animals deficient for gamma-interferon receptor. Together, these results suggest that viruses may exacerbate autoantibody-mediated ITP by activating macrophages through gamma-interferon production, a mechanism that may account for the pathogenic similarities of multiple infectious agents.
In a nutshell, people with compromised immune systems, such as CLL patients, are particularly vulnerable to viral, bacterial and fungal infections. These infections can then cause systemic and widespread inflammation and inflammatory cytokine storms, which then cause exaggerated and inappropriate reaction from macrophages which are among the most potent of the killer cells of our immune system. In the presence of an underlying cancer such as CLL, when some of the safety switches have been compromised, the rampaging macrophages can and often do attack red blood cells and platelets, leading to AIHA and ITP. One can consider treating the AIHA by attacking the CLL, as the root cause of immune system malfunction, by therapies such as Rituxan. Or one can introduce a good dose of properly functioning Ig by means of intravenous Ig shots. And one more thing we can consider doing is making sure there is not an underlying infection of some sort, causing widespread and systemic inflammation. Once again, inflammation seems to be something we should avoid. A goosed-up and hyperactive immune system is not something you want, not if you have the safety switches all messed up by an underlying CLL. Logic for using steroid drugs to control AIHA is also based on this principle of reducing inflammation. As you probably know, steroids are very good at immune suppression, which is one way of reducing inflammation. Just to make this possible connection between activated and out-of-control macrophages killing innocent red blood cells and platelets, etc., there is a name for this: it is called "Hemophagocytic Syndrome" and infection by a whole list of different viruses is very much implicated in this process. Here are some of the viruses that may be involved and of which you might have heard: Herpes, Epstein-Barr, Hepatitis, influenza, cytomegalovirus, the simple adenovirus, for Pete's sake! The two links below are from the Center for Disease Control, very credible, and present a huge amount of information to read. http://www.cdc.gov/ncidod/eid/vol6no6/fisman.htm;
In previous articles on our website we discussed the role of Chronic Inflammation in CLL, and What You Can Do About It. Here is another interesting connection, between vitamin D3 and inflammation. Healthy levels of vitamin D3 provide a negative feedback control on macrophage activation, and reduce inflammation. Think of it this way: when there is too little vitamin D3, there is a tendency for macrophages to get activated, so that they can help make more vitamin D3. Take away this need, and you take away some of the drive for macrophage activation. In lay terms, good vitamin D3 levels decrease the level of activation of macrophages and inflammation. You may want to read again our recent article, Vitamin D3: Essential for Health, and the chronically low levels of this important vitamin in huge percentage of our population. This problem is now near epidemic levels, according to many nutritional researchers.
Cell Mol Biol (Noisy-le-grand). 2003 Mar;49(2):277-300.
The immunological functions of the vitamin D endocrine system.
Hayes CE, Nashold FE, Spach KM, Pedersen LB.
Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, Wisconsin
The discoveries that activated macrophages produce 1alpha25-dihydroxyvitamin D3 (1alpha,25-(OH)2D3), and that immune system cells express the vitamin D receptor (VDR), suggested that the vitamin D endocrine system influences immune system function. In this review, we compare and contrast how 1alpha,25-(OH)2D3 synthesis and degradation is regulated in kidney cells and activated macrophages, summarize data on hormone receptor function and expression in lymphocytes and myeloid lineage cells, and discuss how locally-produced 1alpha,25-(OH)2D3 may activate a negative feed-back loop at sites of inflammation. Studies of immunity in humans and animals lacking VDR function, or lacking vitamin D, are viewed to gain insight into the immunological functions of the vitamin D endocrine system. The strong associations between poor vitamin D nutrition, particular VDR alleles, and susceptibility to chronic mycobacterial infections, together with evidence that 1alpha,25-(OH)2D3 served as a vaccine adjuvant enhancing antibody-mediated immunity, suggest a model wherein high levels of 1alpha,25-(OH)2D3-liganded VDR transcriptional activity may promote the CD4+ T helper 2 (Th2) cell-mediated and mucosal antibody responses to cutaneous antigens in vivo. We also review a diverse and rapidly growing body of epidemiological, climatological, genetic, nutritional and biological evidence indicating that the vitamin D endocrine system functions in the establishment and/or maintenance of immunological self tolerance. Studies done in animal models of multiple sclerosis (MS), insulin-dependent diabetes mellitus (IDDM), inflammatory bowel disease (IBD), and transplantation support a model wherein the 1alpha,25-(OH)2D3 may augment the function of suppressor T cells that maintain self tolerance to organ-specific self antigens. The recent progress in infectious disease, autoimmunity and transplantation has stimulated a gratifying renaissance of interest in the vitamin D endocrine system and its role in immunological health.
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