[Clinical significance and pathogenesis of drug- or microbe-induced autoimmune hemolytic anemias].

Methyldopa and several other drugs, continuously taken over months or years, may induce autoimmunity in persons having a probably genetic predisposition. The autoimmunity is reversible after discontinuation of the drug. A number of infectious agents may lead to the same effect. The autoantibodies can react with different autologous targets, for instance red blood cells. This may occasionally cause an autoimmune haemolytic anaemia. The two pathogenetic cardinal points are discussed in the case of the methyldopa-induced autoimmune haemolytic anaemia: the induction of the process results very probably by inhibiting or blocking of the competent suppressor-T-lymphocytes, which normally prevent an autoantibody production, representing a form of chemical "contrasuppression". This has been demonstrated in cultures of peripheral human blood lymphocytes of patients on methyldopa therapy. The second pathogenetic cardinal point is the effect of the autoantibody after its binding to the drugs investigated up to now. Rarely it is pathogenic. This relation is exactly contrary to the idiopathic warm autoantibody anaemia and remains an unsolved problem. A reversible selective deficiency of suppressor-T-cells has also to be postulated for other autoimmune haemolytic anaemias and autoimmune diseases induced by drugs or infectious agents.