Lymphocyte reactivity to mitogens in American visceral leishmaniasis.

In vitro lymphocyte reactivity to phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) was evaluated in 11 patients with American visceral leishmaniasis (AVL) and 11 control subjects. The diagnosis of AVL was established by the demonstration of leishmania in bone marrow aspirates. Thymidine incorporation (cpm +/- SEM) of PHA-stimulated cultures was 27, 520 +/- 4,488 in the AVL patients and 56,531 +/- 8,787 in the controls (P less than 0.01). No significant difference was observed in the response to Con A and PWM between AVL and control patients. The restoration of the PHA response to levels similar to normal was observed when cells from five AVL patients were cultured in medium supplemented with standard AB serum rather than autologous serum. In this group of experiments the average suppressor activity of the PHA response present in sera from AVL patients was 46%. Lymphocyte reactivity of normal subjects to PHA was also suppressed by the AVL serum: PHA-stimulated lymphocytes cultured in standard AB serum were 49,122 +/- 9,345 vs 23,115 +/- 4,935 cpm in cultures supplemented with AVL serum. The demonstration that AVL serum suppressed the PHA response indicates that some of the cellular immunological abnormalities in AVL patients may be dependent on inhibitor factory present in AVl serum.