CD13 regulates dendritic cell cross-presentation and t cell responses by inhibiting receptor-mediated antigen uptake (106.16)

Abstract

Abstract Dendritic cell (DC) antigen cross-presentation is generally associated with immune responses to tumors and viral antigens and enhancing this process is a focus of tumor vaccine design. In this study, we found that the myeloid cell surface peptidase CD13 is highly and specifically expressed on the subset of DCs responsible for cross-presentation, the CD8+ murine splenic DCs. In vivo studies indicated that lack of CD13 significantly enhanced T cell responses to soluble OVA antigen, although the development, maturation, antigen processing and presentation of DCs is normal in CD13KO mice. In vitro studies showed that CD13 regulates receptor-mediated, dynamin-dependent endocytosis of antigens such as OVA and transferrin but not fluid-phase or phagocytic antigen uptake. CD13 and antigen are co-internalized in DCs but CD13 did not co- immunoprecipitate with antigen receptors, suggesting that CD13 does not control internalization of specific receptors but regulates endocytosis at a more universal level. Mechanistically, we found that phosphorylation of the endocytic regulators p38MAPK and Akt was dysregulated in CD13KO DCs and blocking these kinases perturbed CD13-dependent endocytic uptake. Therefore, CD13 is a novel endocytic regulator that may be exploited to enhance antigen uptake and T cell activation to improve the efficacy of tumor-targeted vaccines.