The antigens that specifically regulate human gamma delta T cell activity have largely remained undefined. Our characterization of CD1d-lipid reactive gamma delta T cells in human blood has provided an initial insight into the signals that Vd1 gamma delta T cells respond to and demonstrated that some gamma deltas rely on MHC antigen presentation.  We have continued to study the antigen reactivity of these cells, exploring their lipid reactivity, MHC restriction and molecular interactions.  We have also demonstrated that CD1d reactive gamma deltas are present in human mucosal tissues and tumors.