ELEVATED PLASMA-LEVELS OF IGE IN PLASMODIUM FALCIPARUM-PRIMED INDIVIDUALS REFLECT AN INCREASED RATIO OF IL-4 TO INTERFERON-GAMMA (IFN-GAMMA)-PRODUCING CELLS

People living in Plasmodium falciparum-endemic areas frequently have e levated levels of total as well as P. falciparum-specific serum IgE. T his study aimed at investigating whether the elevated serum IgE levels reflect a shift in the balance between CD4(+) T helper 1 (Th1) and T helper 2 (Th2) cells in individuals naturally exposed to the P. falcip arum parasite. To investigate the role of Th 1 and Th2 cells in the hu man P. falciparum system we used the ELISPOT assay to determine the ra tio of IFN-gamma- and IL-4-producing cells after specific antigen or m itogen activation in vitro. The donors were individuals who had acquir ed immunity through natural exposure to the parasite. In response to t he specific malaria antigens, very few IL-4-producing cells were seen. However, in the response of individual donors to the polyclonal T cel l activator, leucoagglutinin (La), the anti-malarial IgE levels in pla sma were correlated with an increased ratio of IL-4/IFN-gamma producin g cells. Thus, donors with ratios of IL-4/IFN-gamma > 1 exhibited mean plasma anti-malarial IgE levels significantly greater than those with ratios < 1. In individuals not living in P. falciparum-endemic areas the ratio of IL-4/IFN-gamma was always < 1. Taken together, our data s uggest a shift in the balance between Th1 and Th2 cells in naturally P . falciparum-primed individuals, associated with elevated anti-P. falc iparum plasma IgE levels. The role and biological significance of IgE (Th2-type immune response) for protection against P. falciparum and/or pathogenesis of malaria require further study.