Characterization of γδ T cell subsets in organ transplantation: γδ T cells in allograft transplantation

P>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.