Pathogenesis of cyclosporin A-induced autoimmunity: absence of T-cell reactivity towards syngeneic antigen presenting cells

Autoimmune complications after hematopoietic stem cell transplantation in children with nonmalignant disorders

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) remains the only curative treatment for many nonmalignant disorders, such as autoimmune disorders, inborn metabolic disorders, hemoglobinopathies, and immunodeficiency disorders. Autoimmune complications (AICs) after HSCT, such as autoimmune cytopenias, autoimmune hepatitis, primary biliary cirrhosis, and autoimmune cutaneous manifestations, are still neither well defined nor characterized.

PATIENTS

Between 2000 and 2012, 92 patients (47 males, 45 females) were treated with HSCT in our hospital, 51 with congenital hemoglobinopathies, 19 with primary immunodeficiency disease, 10 with metabolic disorders, five with Fanconi anemia, three with aplastic anemia, and four with familial hemophagocytic lymphohistiocytosis.

RESULTS

Mean age at HSCT was 6.4 years (range, 0.2-32 years) and mean duration of followup after HSCT was 6.81 years (range, 1-11 years). Sixteen (17.4%) patients developed chronic GVHD and five (5.4%) showed sclerodermatous features. Five (5.4%) patients were diagnosed with scleroderma manifestations, six (6.5%) with vitiligo, six (6.5%) with autoimmune hemolytic anemia (AIHA), six (6.5%) with idiopathic thrombocytopenia, three (3.3%) with mild leucopenia, two (2.2%) with aplastic anemia, two (2.2%) (one boy, one girl) with autoimmune thyroid disease, and one (1.1%) with autoimmune hepatitis.

CONCLUSIONS

It was concluded that AICs are clinically significant complications after HSCT that contribute to morbidity but not to mortality. AICs are more frequent after HSCT for metabolic disorders, and sclerodermatous GVHD is more significant in children who underwent allogeneic HSCT for hemoglobinopathies. The potential to identify risk factors for AICs could lead to less morbidity and mortality and to maintain the patient's quality of life.

Ablation and regeneration of tolerance-inducing medullary thymic epithelial cells after cyclosporine, cyclophosphamide, and dexamethasone treatment

Immunosuppressive drugs and cytotoxic chemotherapy agents are designed to kill or suppress autoreactive, alloaggressive, or hyperinflammatory T cells, or disseminated malignancies. However, they also cause severe immunological side effects ranging from interrupted thymopoiesis and general immunodeficiency to, paradoxically, autoimmunity. Consistent with the cross-talk between thymocytes and stromal cells, we now show that these common therapeutic agents have major effects on murine thymic epithelial cells (TEC), crucially required to rebuild immunity posttreatment. We show that the immunosuppressant cyclosporine A, which has been linked to a thymus-dependent autoimmune syndrome in some patients, causes extensive loss of autoimmune regulator (Aire(+)) tolerance-inducing MHC class II(high) medullary TEC (mTEC(high)). Post-cyclosporine A, Aire expression was restored within 7 days. Full recovery of the mTEC(high) subset occurred within 10 days and was linked to a decrease in a relatively resistant MHC class II(low) mTEC subset (mTEC(low)), consistent with a previously described precursor-product relationship. Cyclophosphamide and dexamethasone caused more extensive ablation of thymocytes and stromal cells but again severely depleted tolerance-inducing mTEC(high). Together, these data show that Aire(+) mTECs are highly sensitive to damage and that mTEC regeneration follows a conserved pattern regardless of the treatment regimen used.

Splenectomy for Severe Autoimmune Cytopenias after Allogeneic Stem Cell Transplantation: Case Report

Autoimmune cytopenias are rare but serious complications after hematopoietic stem cell transplantation (HSCT). We per-formed splenectomy in 2 patients who had severe autoimmune cytopenias after allogeneic HSCT (allo-HSCT) that were resist-ant to immunosuppressive treatment. The first patient underwent unrelated allo-HSCT for chronic granulocytic leukemia(CGL) in July 2000. Seven months later, red blood cell and platelet counts went down. The results of a direct Coombs test were intermittently positive. The patient was resistant to therapy with steroids and high-dose immunoglobulin. After a splenectomy was performed in February 2001, the hemoglobin concentration and platelet count improved. Her blood counts remained stable, with a hemoglobin level of approximately 110 g/L and a platelet count >100 x 109/L. She continued therapy with itraconazole, valacyclovir, and penicillin. Some months later, the patient was readmitted for fulminant septic infection, which had a fatal outcome. The second patient underwent related allo-SCT for CGL in January 2003. Seven months later, he was readmitted for intraocular bleeding accompanied by severe thrombocytopenia with antiplatelet antibodies. The patient was resistant to steroid and high-dose immunoglobulin therapy. A splenectomy was performed in September 2003. His platelet count normalized and remains stable. The patient continues therapy with itraconazole, valacyclovir, and penicillin and has not experienced any serious infection. We assume that splenectomy is an effective treatment for resistant immune cytopenias after allo-HSCT. However, severe late infections can compromise the outcome.

A causal link between lymphopenia and autoimmunity

It is well recognized that the composition of the mature T cell population is subject to strict homeostatic control. The TCR repertoire and relative proportions of various T cell subsets are established in the thymus, and continue to be shaped and regulated in the periphery. As the thymic function declines, peripheral homeostatic mechanisms assume increasing importance. Indeed, loss of thymic function does not lead to progressive decline of T cell numbers because peripheral mechanisms ensure that the size of the T cell population is maintained due to proliferation of residual cells. However, our current understanding of the basic mechanisms of 'homeostatic' or lymphopenia-induced proliferation suggests that this drive to maintain population size may be accompanied by loss of TCR diversity and emergence of auto-reactive effector T cells. This prediction is supported by experimental and clinical evidence. This consideration is important because lymphopenia is seen commonly in clinical practice as a consequence of viral infections, or medical treatment of cancer, autoimmunity, and graft rejection. Lymphopenia may be a simple link between viral infections and autoimmunity, and may be one reason for common failure of very potent, but non-specific, immunosuppressive drugs in current clinical use.

Response to steroids in de novo autoimmune hepatitis after liver transplantation

Graft dysfunction associated with autoimmune phenomena has been recently described in liver transplant recipients without previous autoimmune disease. However, the natural history, diagnostic criteria, and definitive therapeutic approach of de novo autoimmune hepatitis (de novo AIH) are poorly understood. We report 12 cases of de novo AIH 27.9 +/- 24.5 months after liver transplantation: the outcome of 7 patients treated with steroids is compared with a group of 5 nontreated patients. Nontreated patients lost the graft after 5.8 +/- 2.6 months from de novo AIH onset. All treated patients were alive after 48.4 +/- 14 (29-65) months from de novo AIH onset, and none of them lost the graft. However, 5 patients relapsed in relation to steroid tapering. All patients presented an atypical antiliver/kidney cytosolic autoantibody, associated to classical autoantibodies in 10 cases. Histological study showed several degrees of lobular necrosis and inflammatory infiltrate. HLA antigen frequencies and matching were compared with 2 control groups (16 orthotopic liver transplantation [LTX] patients without de novo AIH and 929 healthy blood donors); de novo AIH patients showed a higher prevalence of HLA-DR3 (54.5% vs. 25.9%, P =.04) than healthy controls, which was not observed in LTX patients without de novo AIH. In conclusion, this new disease should be included in the differential diagnosis of unexplained graft dysfunction. In addition, treatment with steroids results in a dramatically improved outcome. However, maintenance therapy is usually required.

Successful treatment of thrombocytopenia and hemolytic anemia with IvIG in a patient with lupus-like syndrome after mismatched related PBSCT

Hematopoietic stem cell transplantation (HSCT) is a treatment option for autoimmune diseases but can also cause clinical features similar to those of autoimmune diseases. In some of these cases the autoimmune-like condition is associated with autoimmune cytopenia, a complication that can be unresponsive to established treatment strategies and which may be fatal. The majority of cases reported on immune hemolytic anemia have been of alloimmune origin due to ABO red blood cell antigen incompatibilities between donor and recipient. We now report a patient with a lupus-like syndrome, presenting with severe thrombocytopenia and hemolytic anemia 9 months after HLA-mismatch, ABO compatible-related PBSCT who experienced no response to high-dose steroids, but who had a sustained response to repeated IvIG therapy.