γδ T cells of the murine vagina: T cell response in vivo in the absence of the expression of CD2 and CD28 molecules

Abstract

While little is known about their activation requirements and function, the intraepithelial T cells of the murine vagina express TCR complexes in which the antigen recognition components and the signaling components have unusual features. These vaginal T cells express an invariant V(γ)4/V(δ)1 TCR and appear to be the only intraepithelial γδ T cells that exclusively use FcR γ chains in their TCR complex, To further characterize the vaginal γδ T cells we isolated them from normal mice and from mice injected systemically with an activation-inducing dose of anti-TCR mAb. The isolated γδ T cells were examined by flow cytometry for their surface expression of a panel of adhesion proteins, activation antigens and cellular interaction molecules (CD44, CD62L, CD45RB, LFA-1, CD2 and CD28). The patterns of expression observed indicate that the vaginal γδ T cells of normal mice show the phenotype of effector T cells. The adhesion/co-stimulatory molecules CD28 and CD2 were not detected on vaginal γδ T cells, an interesting finding since the absence of CD2 from other T cells has been suggested to result in anergy. However, vaginal γδ T cells are responsive to TCR-mediated signals since injection of normal mice with pan-anti-TCR antibody or stimulating anti-γδ TCR antibody resulted in an increase in cell number and increased expression of transferrin and IL-2 receptors. These results indicate that vaginal γδ T cells might utilize other co-stimulatory molecules, if any, in connection with TCR-induced activation and differentiation. While the physiological function of vaginal γδ T cells remains unknown, the expression of an invariant V(γ)4/V(δ)1 TCR, their exclusive use of γ chain homodimers in their TCR, and the absence of CD2 and CD28 co-stimulatory molecules are a novel combination of properties that suggests specialized functional properties. Although vaginal γδ T cells share some features in common with γδ T cells that reside in other epithelial tissues, such as skin and intestine, the present studies provide additional evidence that vaginal γδ T cells are a highly specialized and distinct T cell population.