Plasmodium falciparum merozoites primarily stimulate the V gamma 9 subset of human gamma/delta T cells.

Peripheral blood-derived T cells from six unprimed caucasian donors were tested for the in vitro reactivity to Plasmodium falciparum merozoites (PFM). Without exception vigorous proliferative responses were observed within the donors tested. The frequency of PFM-reactive T cells ranged from 1/150-1/300. Phenotypic analysis of peripheral blood lymphocytes cultured in the presence of PFM revealed the preferential outgrowth of gamma/delta T cells, which represented within 7 days about 70% of the reactive T cell blasts. All reactive gamma/delta T cell blasts displayed the V gamma 9+ TcR phenotype. We conclude that human gamma/delta T cells respond vigorously to PFM, and that this property is confined to V gamma 9+ T cell subset.