Immune response in patients during and after Plasmodium falciparum infection.

The kinetics of indicators of lymphocyte activation were determined in non- and semiimmune patients with uncomplicated Plasmodium falciparum infection and in control subjects in Acre, Brazil. Delayed type hypersensitivity (DTH) to seven recall antigens was weakest in nonimmune patients. Both patient groups differed significantly from controls on admission (P less than .001 for both) and improved considerably after clindamycin therapy. Total serum IgG and IgM, but not antimalarial antibodies, were highest in nonimmune patients compared with semiimmune patients and controls during acute malaria. Immunoglobulin levels normalized after chemotherapy. A striking decrease of CD4+ peripheral blood lymphocytes, normalizing after chemotherapy, was seen in both patient groups, and was more pronounced in nonimmune patients. A slight increase in interleukin-2 receptor (IL-2R)-bearing cells was found in nonimmune patients. In addition, soluble plasma IL-2R was significantly elevated in them (P less than .001) and to a lesser extent in semiimmune patients. These findings were paralleled by significantly decreased IL-2 concentrations in plasma (P less than .001) during the acute phase of malaria, suggesting pronounced general immunosuppression in nonimmune malaria patients.