Suppression of Parasite‐Specific Response in Plasmodium falciparum Malaria. A Longitudinal Study of Blood Mononculear Cell Proliferation and Subset Composition

Abstract

The present longitudinal study was designed to characterize immunosuppression during acute Plasmodiu, falciparum infection, during the treatment and up to 1 month after the acute stage. The proliferative responses of blood mononuclear cells (BMNC) isolated from non-immune and semi-immune malaria patients and controls to mitogens and two Plasmodium-derived stimulators (merozoites, Meroz. and soluble purified antigen, Spag) and non-related antigens were measured by [² H]thymidine incorporation. BMNC isolated before treatment (day 0) from the non-immune patients did not respond to Meroz, whereas those from controls showed a significantly higher response. The SPag responses were also low in BMNC isolated on day 0 and increased in both the non-immune and the semi-immune patients during the observation period. These findings indicate that during malaria there is a depression of the parasite-specific proliferative response. The subset composition of BMNC isolated from non-immune patients was studied in a FACS analyser. The mean cell volumes of both Leu 2’and Leu.3 cells were increased during the acute phase of the infection, indicating that malaria infection results in activation of both T-helper and T-suppressor cells. There was no overall reduction of the response to mitogens on day 0. However. 3 days alter initiation of the treatment the mitogen response was decreased.‘This finding indicates that it is important to distinguish between the effects of malaria infection and of drug treatment.