Functional difference between Thy-1-positive and Thy-1-negative γδ T cells induced by Escherichia coli infection in mice

There is an increase in number of γδ T cells in the peritoneal cavity after intraperitoneal (i.p.) inoculation with Escherichia coli. The E. coli- induced γδ T cells in C3H/He mice contain a large amount of Thy-1-negative population in addition to the Thy-1-positive population. We investigated the difference between the Thy-1-positive and the Thy-1-negative γδ T cells. Although it was found that only up to 4% of the γδ T cells on day 5 after infection were in cycling phase, and that the γδ T cells did not proliferate by immobilized anti-T-cell receptor (TCR) γδ monoclonal antibody stimulation, the γδ T cells proliferated in the presence of interleukin-2 (IL-2) and IL-7. The Thy-1-negative γδ T cells showed higher proliferative response compared with the Thy-1-positive γδ T cells. Furthermore, the Thy-1-negative γδ T cells showed lower IFN-γ mRNA expression than the Thy-1-positive γδ T cells. On the other hand, both the Thy-1-positive and Thy-1-negative γδ T cells predominantly expressed Vγ1, Vγ4, Vγ5, Vγ6 and Vδ1, and no difference of V region usage was detected between them. These results suggest that functions of Thy-1-positive γδ T cells differ from Thy-1-negative γδ T cells although Thy-1-positive and Thy-1-negative γδ T cells may have similar V region repertoire and, possibly, similar antigen specificity.