Characterization of [gamma][delta] T cell subsets in organ transplantation

Summary [gamma][delta] T cells are innate-type lymphocytes that preferentially act as regulators of local effector immune responses. Recent reports found an altered distribution of the two main subpopulations of blood [gamma][delta] T cells (V[delta]1 and V[delta]2) in operationally tolerant liver transplant recipients. Based on this, [gamma][delta] T cells subset quantification was proposed as a biomarker of immunologic risk in liver transplantation. The specific characteristics of [gamma][delta] T cell subsets in transplantation remain however unknown. We have investigated here the phenotype, repertoire and functional properties of [gamma][delta] T cell subsets in a large population of allograft recipients. Our results indicate that alterations in the [gamma][delta] T cell compartment are not restricted to tolerant liver recipients. In fact, most immunosuppressed liver and kidney recipients also display an enlarged peripheral blood [gamma][delta] T cell pool mainly resulting from an expansion of V[delta]1 T cells exhibiting an oligoclonal repertoire and different phenotypic and cytokine production traits than V[delta]2 T cells. We propose that persistent viral infections are likely to contribute to these alterations. Our data provide novel insight in the biology of [gamma][delta] T cells and a rationale for exploring these lymphocytes in more depth into the pathogenesis of viral infections in transplantation.