Phenotypic profile and functional characteristics of human gamma and delta T cells during acute toxoplasmosis.

Gamma and delta (gamma delta) T-cell receptor lymphocytes are increased during acute toxoplasmosis. These cells are BB3+ CD45RO+ CD8-. Purified gamma delta T cells failed to proliferate in response to Toxoplasma gondii antigen (stimulation index, 1.4 +/- 0.6) but were responsive to phytohemagglutinin stimulation (stimulation index, 20.8 +/- 1.9). Natural-killer-like cytotoxicity was strongly acquired only after in vitro culture of purified gamma delta T cells with recombinant interleukin 2 (40% +/- 7% specific lysis). Our data show that gamma delta T-cell receptor T cells with a peculiar phenotype are increased during human acute T. gondii infection.