Aplastic anaemia: Evidence for an immunological mechanism.

The soft agar culture assay (C.F.U.-C) has been used in vitro as a measure of haemopoietic capacity of bone-marrow. In a patient with aplastic anaemia pretreatment of the patient's bone-marrow with horse anti-human-thymocyte globulin and complement (A.T.G. + C) prior to culture led to a dramatic increase in ability to form colonies in the soft agar assay; and co-culturing marrow from a normal donor and from the patient resulted in a distinct reduction in the number of expected C.F.U.-C. These findings point ot an immunological or autoimmune mechanism in this patient by selective destruction of the suppressing cells in the patient's marrow with A.T.G. and by suppression of normal myelopoiesis following addition of the patient's marrow to normal marrow.