Immunologic mechanisms in aplastic anemia.

The existence of abnormalities of the immune system in patients with aplastic anemia is controversial. Review of the evidence for immune deficiency as a component of the aplastic process in these patients reveals generally intact lymphocyte function, but a variable degree of monocyte impairment. Evidence is presented that excessive T-lymphocyte activity may be implicated in the pathogenesis of aplastic anemia, but this complicated by the possible induction of such suppressor cells in response to blood transfusions.