Study of lymphocyte populations and natural killer activity in severe aplastic anaemia.

Thirty-one patients (pts) with aplastic anaemia (AA) were studied whose probable etiology were: idiopathic (16 pts), nocturnal aroxysmal haemoglobinuria (NPH) (2 pts), benzene (4 pts), agrotoxics (5 pts), pharmaceutical drugs (2 pts) and insecticides (2 pts). A decrease in total lymphocyte counts was seen in 10 pts belonging mainly to the NPH and pharmaceutical drug groups, whereas, in the benzene group the opposite was found. B cell levels were low in 9 out of 20 pts. T cell levels varied, the majority of patients had normal levels, 13 presented low levels and 4 had increased numbers. CD4 levels were low in 14 pts and T cell numbers were compensated in some by an increase in CD8 cells. Our results show that there is a great heterogeneity among the patients and there might be differences in the immunological profile of aplastic anaemia depending on the causative agent of the disease.