Immunologic and clinical effects of repeated blood exchange in familial erythrophagocytic lymphohistiocytosis.

Depressed cellular immune function and increased susceptibility to infection characterize familial erythrophagocytic lymphohistiocytosis (FEL), a usually fatal autosomal recessive disease. One component of the immunodeficiency is plasma-mediated inhibition of lymphocyte proliferation. We have tested whether repeated plasma or blood exchange would decrease plasma inhibitory activity and improve cellular immune function in FEL. Following this treatment, reduction in plasma inhibitory activity, reversal of depressed antigen-specific lymphocyte proliferative responses and monocyte antibody-dependent cytotoxic function in vitro, and clinical improvement were complete in two and partial in one of three patients studied. Relapse, which was ultimately fatal, was associated with recurrence of the immune defects. These findings suggest that cellular immunodeficiency in FEL is acquired and possibly related to circulating immunosuppressive activity, the removal of which is associated with transient immunologic and clinical recovery.