Cutting Edge: Allogeneic CD4+CD25+Foxp3+ T Regulatory Cells Suppress Autoimmunity while Establishing Transplantation Tolerance

An important unresolved question with regard to T regulatory (Treg) cell specificity and suppressive activity is whether allogeneic Treg cells inhibit self-reactive T cells. In the present study, this issue was addressed using IL-2Rbeta-deficient mice that develop rapid lethal autoimmunity due to impaired production of Treg cells. We show that adoptive transfer of completely MHC-mismatched Treg cells into IL-2Rbeta(-/-) mice resulted in life-long engraftment of the donor cells, which exhibited skewed reactivity toward host alloantigens, and prevented autoimmunity. Thus, Treg cells that underwent thymic selection by peptide/MHC class II complexes distinct from those recognized by autoreactive T cells, still effectively suppress autoimmunity. Remarkably, when such animals were skin grafted, they exhibited dominant tolerance to those grafts bearing MHC molecules that were shared with donor Treg cells. Collectively, these data demonstrate that effective engraftment by allogeneic Treg cells controls autoimmunity and results in permissive conditions for long-term acceptance of allografts.

A novel human CD32 mAb blocks experimental immune haemolytic anaemia in FcgammaRIIA transgenic mice

A fully human IgG1 kappa antibody (MDE-8) was generated, which recognised Fc-gamma receptor IIa (FcgammaRIIa) molecules on CD32 transfectants, peripheral blood monocytes, polymorphonuclear cells and platelets. This antibody blocked FcgammaRIIa ligand-binding via its F(ab')(2) fragment. Overnight incubation of monocytes with F(ab')(2) fragments of MDE-8 leads to a c. 60% decrease in cell surface expression of FcgammaRIIa. MDE-8 whole antibody induced a concomitant c. 30% decrease of FcgammaRI on THP-1 cells and monocytes. In humans FcgammaRIIa plays an important role in the clearance of antibody-coated red blood cells in vivo. As an equivalent of FcgammaRIIa does not exist in mice, the in vivo effect of MDE-8 was studied in an FcgammaRIIa transgenic mouse model. In these mice, antibody-induced anaemia could readily be blocked by MDE-8. These data document a new human antibody that effectively blocks FcgammaRIIa, induces modulation of both FcgammaRIIa and FcgammaRI from phagocytic cells, and ameliorates antibody-induced anaemia in vivo.

CD4+CD25+ regulatory T cells control induction of autoimmune hemolytic anemia

Autoimmune hemolytic anemia (AIHA) is the result of increased destruction of red blood cells (RBCs) due to the production of autoantibodies, and it can be life-threatening. To study the mechanisms that trigger AIHA, we used the Marshall-Clarke and Playfair model of murine AIHA, in which mice repeatedly immunized with rat RBCs develop erythrocyte autoantibodies as well as rat-specific alloantibodies. We analyzed the role of CD25(+) T-regulatory subsets in controlling AIHA in C57/Bl6 mice using antibody depletion studies. Treatment with anti-CD25 antibody but not isotype control prior to immunization with rat RBCs increased the incidence of AIHA from 30% to 90%. Adoptive transfer of purified splenic population of CD4(+)CD25(+) but not CD4(+)CD25(-) cells from immunized mice into naive recipients prevented the induction of autoantibody production. Altogether, our data establish a critical role for CD4(+)CD25(+) cells for control of AIHA, which may help to establish therapeutic strategies for treatment of AIHA.

Review: complement receptor 1 therapeutics for prevention of immune hemolysis

The complement system plays a crucial role in fighting infections and is an important link between the innate and adaptive immune responses. However, inappropriate complement activation can cause tissue damage, and it underlies the pathology of many diseases. In the transfusion medicine setting, complement sensitization of RBCs can lead to both intravascular and extravascular destruction. Moreover, complement deficiencies are associated with autoimmune disorders, including autoimmune hemolytic anemia (AIHA). Complement receptor 1 (CR1) is a large single-pass glycoprotein that is expressed on a variety of cell types in blood, including RBCs and immune cells. Among its multiple functions is its ability to inhibit complement activation. Furthermore, gene knockout studies in mice implicate a role for CR1 (along with the alternatively spliced gene product CR2) in prevention of autoimmunity. This review discusses the possibility that the CR1 protein may be manipulated to prevent and treat AIHA. In addition, it will be shown in an in vivo mouse model of transfusion reaction that recombinant soluble forms of CR1 can reduce complement-mediated RBC destruction, thereby prolonging survival of transfused RBCs. It is proposed that CR1-based therapeutics have potential for effective and safe prophylactic short-term use and for treatment of hemolytic transfusion reactions.

Transgenic Expression of CTLA-4 Controls Lymphoproliferation in IL-2-Deficient Mice

IL-2-deficient mice develop a lymphoproliferative and autoimmune disease characterized by autoimmune hemolytic anemia (AHA) and inflammatory bowel disease. We have previously reported that IL-2 is necessary for optimal up-regulation of CTLA-4, an inducible negative regulator of T cell activation. In this study, we have tested the hypothesis that reduced expression of CTLA-4 in IL-2-deficient T cells contributes to the pathogenesis of disease in IL-2-deficient mice. Expression of CTLA-4 as a transgene completely prevented lymphoaccumulation and AHA in IL-2-deficient mice. The normalization of T cell numbers was due to inhibition of expansion of conventional CD4+CD25- T cells rather than to rescue of the numbers or function of CD4+CD25+ regulatory T cells, suggesting that CTLA-4 expression on conventional T cells plays a role in maintaining normal T cell homeostasis. In addition, the inhibitory effect of the CTLA-4 transgene on T cell expansion was at least in part independent of CD28 expression. Our results suggest that deficient CTLA-4 expression on conventional T cells contributes to the pathophysiology of the lymphoproliferative disease and AHA in IL-2-deficient mice. Thus, restoring CTLA-4 expression in T cells may be an attractive strategy to control clinical autoimmune diseases in which CTLA-4 expression is reduced.

Beneficial effect of a human monoclonal IgM cryoglobulin on the autoimmune disease of New Zealand black mice

NZB mice spontaneously develop an autoimmune disease characterized by autoimmune hemolytic anemia, thymic atrophy, lymphoid hyperplasia, and hypergammaglobulinemia. The aim of this study was to examine the hypothesis that cryoglobulins may have an immunoregulatory effect on the autoimmune process. The effect of human monoclonal IgM cryoglobulin preparations (including Cryo13, Cryo14, and Cryo16) isolated from the serum of patients with Waldenström's macroglobulinemia on the autoimmune disease of NZB mice was therefore studied. The effect of cryoglobulin preparations was evaluated on several disease parameters, i.e., survival, severity of anemia, and serum IgM and IgG levels (hypergammaglobulinemia). We found that immunization of NZB mice with Cryo13 at 3 months of age delayed the course of the disease, whereas Cryo14 and Cryo16 were ineffective. Furthermore, the effect of Cryo13 was long lasting. On the other hand, Cryo13 was able to react with 8 of 32 mouse monoclonal natural IgM autoantibodies. In contrast, Cryo14 was able to bind only 2 and Cryo16 none of these mouse monoclonal IgM antibodies. These results indicate that, in this model of autoimmune pathology, the beneficial effect of Cryo13 is mediated by its idiotypic interaction with the murine natural autoantibody network.

Autoimmune hemolytic anemia in patients with SCID after T cell-depleted BM and PBSC transplantation

We report a high incidence (19.5%) of autoimmune hemolytic anemia (AIHA) in 41 patients with SCID who underwent a T cell-depleted haploidentical transplant. Other than infections, AIHA was the most common post-transplant complication in this patient cohort. Clinical characteristics and treatment of eight patients who developed AIHA at a median of 8 months after the first T cell-depleted transplant are presented. All patients had warm-reacting autoantibodies, and two of eight had concurrent cold and warm autoantibodies. Clinical course was most severe in two patients who had cold and warm autoantibodies. Five patients received specific therapy for AIHA. Successful taper off immunosuppressive therapy for AIHA coincided with T cell reconstitution. Delayed reconstitution of T cell immunity, due to T cell depletion, immunosuppressive conditioning and CsA, as well as paucity of regulatory T cells, are the likely explanations for the occurrence of AIHA in our patient cohort. Screening of the population at risk may prevent morbidity and mortality from AIHA.

Interleukin-2 is indispensable for development of immunological self-tolerance

Interleukin-2-deficient mice (IL-2(-/-)) manifest severe immune system abnormalities characterized by an uncontrolled activation and proliferation of lymphocytes. A systemic autoimmune syndrome results, and hemolytic anemia leads to early death especially in mice derived from a BALB/c genotype. Remarkably, IL-2 treatment prevents both the activation of the immune system and the development of autoimmune disease. Moreover, adoptive transfer of lymphocytes from IL-2-treated IL-2(-/-) animals confers protection to IL-2(-/-) mice, suggesting that IL-2 induces a postnatal differentiation/maturation of regulatory cells necessary for self- and non-self-discrimination.

Successful control of refractory and life-threatening autoimmune hemolytic anemia with intravenous immunoglobulins in a man with the primary antiphospholipid syndrome

A 58-year old man with a history of hypothyroidism and primary antiphospholipid syndrome (with recurrent thromboembolic disease and therapy-refractory autoimmune thrombocytopenic purpura) presented with a life-threatening crisis of warm autoimmune hemolytic anemia (AIHA) while under chronic low-dose steroid therapy. The exacerbation was eventually controlled with a 5-day course of intravenous immunoglobulin (IVIG, Sandoglobulin) (400 mg/kg per day) but hemolysis rapidly recurred, despite therapy with steroids, azathioprine, and cyclosporin, necessitating a second course of IVIG. Control of packed cell transfusion needs for about 7 months was achieved by weekly administration of IVIG (800 mg/kg), although there is no direct evidence that IVIG therapy reduced the production of anticardiolipin or RBC antibodies. Three months after discontinuation of IVIG and change to maintenance with intermediate-dose corticosteroids plus cyclosporin A, the patient succumbed to duodenal perforation with peritonitis and invasive pulmonary aspergillosis. The case illustrates that IVIG therapy may be helpful in selected life-threatening and refractory cases of AIHA. It also sadly illustrates the long-term toxicity of standardly used therapeutics in refractory AIHA.

Acceleration of thrombosis and hemolysis by fibrinolysis inhibiting factor and suppression by Ia antigen expressed on T cells in partially hepatectomized Lewis rats

Partial hepatectomy (PH) of a left lateral lobe was performed on 45 Lewis rats 6.5-8.0 weeks old. Splenectomy, the injection of a fibrinolysis inhibiting (F1) factor (Gly-Pro-Arg-Pro) and both treatments were combined with the PH in 10, 11 and 9 rats, respectively. Among them, 4 males became weak with marked atrophic thymus before the 46th day after PH. All these males had massive pulmonary necrosis accompanied by platelet-rich emboli. Erythrocyte rosette formation was recognized in the mesenteric lymph nodes (MLN) of all 4 rats. The rosette erythrocytes reacted to anti-macrophage antibodies. FI factor-induced acute immune hemolysis occurred 5-9 days after PH in the 2 of the FI factor-injected and splenectomized males. Mildly to moderately atrophic thymuses were found in almost all the rats followed for 156-177 days after PH. T lymphocytes with cytoplasmic dense polysomes and desquamating endothelial cells with phagocytic erythrocytes were observed in the thymic electron micrograph of the FI factor-injected female. Positive D-D dimers were measured in the plasma of 7 rats. Increased peripheral reticulocytes (7.0 +/- 0.4%) were recognized in the males 156 days after single PH but not in the females. Ten of the 24 females and 3 of the 16 males showed an increase of peripheral Ia+ T cells to 20-30%. As well as acute pulmonary emboli, autoimmune hemolysis was induced more actively after PH in the males with CD5+ T cells that expressed the Ia antigen weakly.

Prevention of autoimmune symptoms in autoimmune-prone mice by elimination of B-1 cells

Our recent studies on an autoantibody-transgenic mouse line demonstrated that peritoneal B-1 cells are responsible for autoimmune symptoms. However, whether B-1 cells in the peritoneum are generally involved in the pathogenesis of autoimmune disease remains controversial. To test the possible involvement of peritoneal B-1 cells in autoimmune symptoms of autoimmune-prone NZB mice, we eliminated the peritoneal cells by hypotonic shock with repeated i.p. injection of distilled water every 7 days into neonatal or 8-week-old NZB mice. By this treatment, B-1 cells, which self-renew within the peritoneal cavity, are expected to be preferentially eliminated, while other peritoneal cells can be easily supplied from bone marrows after this treatment. Indeed, in distilled water-treated old NZB mice, the number of B-1 cells decreased in spleen as well as in lamina propria of the gut but the numbers of conventional B cells and T cells did not change. Moreover, the production of autoantibodies against erythrocytes significantly decreased and the occurrence of autoimmune hemolytic anemia was reduced in 12-month-old treated NZB mice. Similarly, the elimination of peritoneal cells of NZB/NZW (NZB/W) F1 mice by water injection decreased anti-DNA IgG antibodies in the sera and reduced the pathological changes of the kidney. These results suggest that peritoneal B-1 cells may be a source of autoantibody-producing cells in autoimmune diseases of NZB and NZB/W F1 mice.

Differential effects of immunisation with mycobacterial 65 kD heat shock protein on two models of autoimmunity

The effects of preimmunisation with the 65 kD mycobacterial heat shock protein (hsp65) on 2 murine models of autoimmunity were compared. Experimental autoimmune haemolytic anaemia (AIHA) can be provoked in mice by repeated injection with rat red blood cells (RBC). In this model, preimmunisation with hsp65 10 days before induction of disease resulted in a partial, but significant, reduction in RBC-bound autoantibody levels measured by Coombs' test. However, preimmunisation with human IgG (hIgG) was associated with a similar suppressive effect. Administration of neither hsp65 nor hIgG affected the direct or indirect anti-rat agglutinin titres of mice subsequently injected with rat RBC. Injection of hsp65 or hIgG prior to induction of AIHA elicited the production of IgG antibodies against the respective immunogen, as judged by enzyme-linked immunosorbent assays. In contrast to the results in experimental AIHA, pristane-induced arthritis (PIA) was effectively prevented by preimmunisation with hsp65, but not with hIgG. It is considered that, whilst hsp65 injection may slightly reduce subsequent anti-RBC autoantibody production in AIHA by antigenic competition, such a mechanism cannot account for the substantial protection against PIA afforded by hsp65 preimmunisation. We suggest that the high, sustained production of anti-hsp65 antibodies observed in mice given hsp65 and pristane may play a role in specifically suppressing arthritogenic immune responses in PIA.

The effect of histamine on the induction of experimental autoimmune hemolytic anemia on OF1, BALB/c and SJL mice

Erythrocyte autoantibodies can be elicited in mice by injection of rat red blood cells (RBC) which are cross-reactive with mouse RBC. In this report, we show that histamine injected in vivo delayed the production of autoantibodies among BALB/c and OF1 mice. In contrast, the induction of autoantibodies in SJL mice was not affected by histamine. Furthermore, histamine did not affect the production of anti-rat RBC. Cimetidine (anti-H2) but not diphenhydramine (anti-H1) inhibited the histamine effect.

Effect of low dietary lipid on the development of Sjögren's syndrome and haematological abnormalities in (NZB x NZW)F1 mice

A diet low in fat was found to retard the development of autoimmune disease in (NZB x NZW)F1 mice, whereas diets high in fat content were associated with more severe disease. The ability of a reduced lipid intake to ameliorate the progression of autoimmune disease was indicated by preserved lacrimal gland secretion (measured by a modified Schirmer test), decreased infiltration of inflammatory cells into the exocrine tissue, and decreased severity of immunohaemolytic anaemia as indicated by near-normal packed cell volume and reticulocyte values. These results suggest that nutritional intervention may be of some help in reducing the severity of pathological abnormalities associated with human systemic lupus erythematosus and Sjögren's syndrome.

Screening for neonatal isohemolytic anemia in calves

Anti-erythrocytic immunoglobulins in serum and colostrum of 124 anaplasmosis-vaccinated cows were detected with a saline agglutination test. Positive results were correlated with the occurrence of neonatal isohemolytic anemia (NIA) in calves and were used to predict the occurrence of NIA. The disease was prevented by withholding colostrum from calves with a high potential for NIA.

Protection against hemolysis in ABO mismatched renal transplantation

The kidneys from a blood group O cadaver donor were transplanted into two patients whose blood groups were B and A2B. The former developed a positive direct antiglobulin test (DAT) and hemolysis due to anti-B; the latter also developed a positive DAT, but due to anti-A. However, this second patient, unlike the first, did not have any hemolysis. Both patients were on the same immunosuppression regimen with cyclosporine. The possible protective roles of patients' ABO subgroup and blood group substances in plasma are discussed.

[Role of immunologic reactions in the development, prevention and treatment of postoperative anemia]

On the basis of an analysis of immunological and hematological indices the authors have shown the role of activation of physiological hemolysis, immunization of the organism by erythrocyte antigens, inhibition of erythropoiesis due to intoxication and massive hemotransfusions in the development of early and late anemias after operations for congenital and acquired heart diseases under conditions of the artificial blood circulation. The authors propose recommendations for the prevention of such anemias.

Anti-A antibody transfused with non-group-specific platelets. Serological abnormalities

In 1979 we identified six patients in blood group A who were given non-group-specific platelets and who had difficulties in pretransfusion testing because of passively acquired antibodies to their own A antigen. In all six, results of earlier pretransfusion testing were unremarkable. Postplatelet transfusion findings consisted of the following: (1) negative result of screening for unexpected antibodies, (2) positive result from direct antiglobulin (Coombs') test, (3) incompatible cross match with group A RBCs, and (4) detection of anti-A antibody in each patient's serum and eluate. No clinical evidence of hemolysis was present in any of the patients. Identification of passively acquired ABO antibodies and selection of compatible blood can be facilitated by (1) accurate review of transfusion history for administration of non-group-specific blood products, (2) testing of eluate against group A, B, and O RBCs, and (3) cross match of patient's sera against group O donor RBCs.

Cytomegalovirus-induced haemolytic anaemia after cardiac surgery

A patient, who underwent aortic valve replacement, developed a transient, autoimmune haemolytic anaemia in association with a significant rise in titre of antibodies against cytomegalovirus. A serological survey of blood donors indicated that the source of infection was fresh blood transfused during and shortly after surgery. A number of cases of short-lived haemolytic anaemia after large volume blood transfusion with cardiac surgery may be explained by this mechanism. It may be preferable to use only blood that has been screened for evidence of recent cytomegalovirus infection if post-perfusion complications of this disease are to be avoided.