Functional Conversion and Dominance of γδ T Subset in Mouse Experimental Autoimmune Uveitis.

We have previously shown that activated γδ T cells have a much stronger proinflammatory effect in the development of experimental autoimmune uveitis than their nonactivated counterparts. Our present study explored γδ T cell subsets are functionally distinct in autoimmune pathogenesis and determined the pathogenic contribution of biased Vγ4+ γδ T cell activation in this disease. By systematically comparing two major peripheral γδ T cell subsets, the Vγ1+ and the Vγ4+ cells, we found that the Vγ4+ cells were readily activated in B6 mice during experimental autoimmune uveitis development, whereas Vγ1+ cells remained nonactivated. Cytokines that were abundantly found in the serum of immunized mice activated Vγ4+, but did not activate Vγ1+, cells. The Vγ4+ cells had a strong proinflammatory activity, whereas the Vγ1+ cells remained nonactivated when tested immediately after isolation from immunized mice. However, when the Vγ1+ cells were activated in vitro, they promoted inflammation. Our results demonstrated that activation is a major factor in switching the enhancing and inhibiting effects of both Vγ1+ and Vγ4+ γδ T cell subsets, and that γδ T cell subsets differ greatly in their activation requirements. Whether the enhancing or inhibiting function of γδ T cells is dominant is mainly determined by the proportion of the γδ T cells that are activated versus the proportion not activated.