In this study, the ability of purified bovine gammadelta T cells in vitro to be activated by superantigens (SAg) was investigated. Freshly isolated WC1(+) gammadelta T cells, in the presence of autologous glutaraldehyde-fixed or gamma-irradiated antigen presenting cells (APC) and IL-2, were incubated with staphylococcal enterotoxins A and B (SEA and SEB), and toxic shock syndrome toxin-1 (TSST-1). Both a proliferative response and the expression of particular T cell receptor genes of the gamma variable (TCR Vgamma) repertoire family were induced. Genes encoding TCR Vgamma1 and TCR Vgamma2 family, but not TCR Vgamma5 were detected. The cells also expressed cytokine transcripts, namely, those of IL-12, IFN-gamma and TNF-alpha, but not IL-2, IL-4, IL-6, IL-7 and IL-10. The activation and proliferation of freshly isolated gammadelta T cells by non-processed antigens required two signals, one originating from the APC and a second dependent on exogenous IL-2. Our results show that purified bovine WC1(+) gammadelta T cells could be driven to proliferate and to express a particular TCRVgamma profile in response to superantigen activation. The possible implication of cytokines expressed by bovine gammadelta T cells in immunopathogenesis is discussed.