GAMMA-DELTA-T-CELLS IN THE PERIPHERAL-BLOOD OF INDIVIDUALS FROM AN AREA OF HOLOENDEMIC PLASMODIUM-FALCIPARUM TRANSMISSION

Gammadelta T cells bearing Vgamma9 T cell receptors from unexposed Cau casian donors make large responses to Plasmodium falciparum in vitro. This finding, together with observations of others showing high levels of Vgamma9+ T cells in the blood of infected non-immune individuals, led us to hypothesize that the response of these cells might contribut e to the pathology of P. falciparum malaria. Acquisition of immunity t o disease in people naturally exposed to infection may therefore be du e in part to down-regulation or alteration of the function of gammadel ta T cells. Supporting this view, and in contrast to infection in non- immune individuals, Vgamma9+ T cells are not elevated in peripheral bl ood of children or adults living in an endemic area despite constant e xposure to P. falciparum. After in vitro stimulation with P. falciparu m, however, the expansion of Vgamma9+ cells from the African donors is of similar magnitude to that observed for non-exposed Europeans. Thus , although these cells are not elevated in peripheral blood, they are still able to respond to P. falciparum antigens. In adult European don ors the major gammadelta T cell population in peripheral blood is Vgam ma9+ (approximately 70% of all gammadelta cells), whereas in the major ity of adult Africans Vdelta1+ Vgamma9- T cells predominated (approxim ately 70% of total gammadelta cells).