Immunosuppressive mechanisms in pure red cell aplasia--a review.

Pure red cell aplasia (PRCA) has been associated with a variety of clinical disorders, and various autoimmune mechanisms have been described to account for the red cell suppression. Primary PRCA occurs via both humoral and cell mediated mechanisms. Recent evidence using gene rearrangement studies indicates PRCA with T-lymphocytosis is a clonal chronic T cell lymphoproliferative disorder in which the T cells suppress erythropoiesis. Called T cell lymphocytosis and cytopenia (TCLC), this disorder has unique features, such as frequent rheumatoid arthritis (RA) and neutropenia. A subset of this disorder with natural killer (NK) like cells also exists, though direct NK cell suppression has not been proven. In secondary PRCA, both humoral and cellular suppression of erythropoiesis have also been described, except in chronic lymphocytic leukemia (CLL) where T cell suppression primarily accounts for the red cell aplasia. A role for the cell-adherent layer of the bone marrow, including macrophages, has also been demonstrated.