ROLE OF CD4-CELLS IN THE EXPANSION OF THE CD4-, CD8- GAMMA-DELTA-T-CELL SUBSET IN THE SPLEENS OF MICE DURING BLOOD-STAGE MALARIA( T)

The previously observed expansion of the splenic gammadelta T cell sub set was examined during the course of murine malaria to determine whet her CD4+ T cells are required. Flow cytometric analysis during the cou rse of Plasmodium chabaudi adami malaria in both C57BL/6 and BALB/c mi ce revealed that the maximal percentage of CD4+ T cells that were blas ts occurred during the period of ascending parasitemia, whereas the ma ximal numbers of gammadelta T cells and blast cells occurred during th e period of descending parasitemia. Transfer of enriched populations o f CD4+ cells (>75%) containing <0.9% gammadelta T cells from immune BA LB/c donor to SCID mice led to a population of gammadelta T cells that constituted 37% of the splenic T cells in the recipients and allowed them to resolve their infections. Transfer of the CD4- fraction did no t suppress parasitemia. These results suggest that CD4+ T cells are ac tivated early during the infection and are required for the subsequent expansion of the gammadelta T cell population. Furthermore, the maxim al gammadelta T cell blast response during the period of descending pa rasitemia and the detection of high levels of these cells only in mode ls that resolved their infections suggest that these cells may functio n in the resolution of blood-stage malaria.