Invariant NKT Cells Promote the Development of Highly Cytotoxic Multipotent CXCR3+CCR4+CD8+ T Cells That Mediate Rapid Hepatocyte Allograft Rejection

Abstract

Hepatocyte transplant represents a treatment for metabolic disorders but is limited by immunogenicity. Our prior work identified the critical role of CD8⁺ T cells, with or without CD4⁺ T cell help, in mediating hepatocyte rejection. In this study, we evaluated the influence of invariant NKT (iNKT) cells, uniquely abundant in the liver, upon CD8-mediated immune responses in the presence and absence of CD4⁺ T cells. To investigate this, C57BL/6 (wild-type) and iNKT-deficient Jα18 knockout mice (cohorts CD4 depleted) were transplanted with allogeneic hepatocytes. Recipients were evaluated for alloprimed CD8⁺ T cell subset composition, allocytotoxicity, and hepatocyte rejection. We found that CD8-mediated allocytotoxicity was significantly decreased in iNKT-deficient recipients and was restored by adoptive transfer of iNKT cells. In the absence of both iNKT cells and CD4⁺ T cells, CD8-mediated allocytotoxicity and hepatocyte rejection was abrogated. iNKT cells enhance the proportion of a novel subset of multipotent, alloprimed CXCR3⁺CCR4⁺CD8⁺ cytolytic T cells that develop after hepatocyte transplant and are abundant in the liver. Alloprimed CXCR3⁺CCR4⁺CD8⁺ T cells express cytotoxic effector molecules (perforin/granzyme and Fas ligand) and are distinguished from alloprimed CXCR3⁺CCR4^-CD8⁺ T cells by a higher proportion of cells expressing TNF-α and IFN-γ. Furthermore, alloprimed CXCR3⁺CCR4⁺CD8⁺ T cells mediate higher allocytotoxicity and more rapid allograft rejection. Our data demonstrate the important role of iNKT cells in promoting the development of highly cytotoxic, multipotent CXCR3⁺CCR4⁺CD8⁺ T cells that mediate rapid rejection of allogeneic hepatocytes engrafted in the liver. Targeting iNKT cells may be an efficacious therapy to prevent rejection of intrahepatic cellular transplants.