[Immune pathophysiology of refractory anemias]

Among different immune pathophysiologies of anemia, those of bone marrow failure syndromes such as aplastic anemia and myelodysplastic syndrome are most difficult to understand. An increase in the proportion of glycosylphosphatidyl-inositol anchored protein-deficient cells has been identified as the best marker for the presence of immune pathophysiology in this elusive syndrome. The significance of detecting small populations of such paroxysmal nocturnal hemoglobinuria (PNH)-type cells was substantiated by a recent observation that PNH-type cells arose from a donor-derived hematopoietic stem cell with a PIG-A mutation in an aplastic anemia patient with late graft failure which responded well to immunosuppressive therapy. Identification of auto-antigens capable of inducing cytotoxic T cells against hematopoietic stem cells is necessary to prove the escape of PIG-A mutant clone from the immune system attack using animal models.