Invariant NKT cells promote expansion of novel CXCR3+CCR4+CD8+ T cells in the liver following allogeneic hepatocyte transplant

Abstract

Abstract Hepatocyte transplant (HcTx) is a treatment for metabolic diseases and a bridge to liver transplant but is limited by immunogenicity. Our prior work identified the critical role of CD4-dependent and CD4-independent CD8+ T cells in HcTx rejection. Herein, we evaluated the influence of invariant natural killer T cells (iNKTs), abundant in the liver, upon CD8+ T cell responses in the presence and absence of CD4+ T cells. To investigate this, C57BL/6 (wild-type; WT) or iNKT deficient Jα18 KO (H-2b) received FVB/N (H-2q) HcTx. Cohorts were depleted of CD4+ T cells and/or reconstituted with iNKTs. Recipients were evaluated for cytotoxicity, CD8+ T cell phenotype, and HcTx rejection. By comparing CD4-sufficient WT and Jα18 KO recipients, we found that the presence of iNKTs significantly enhanced in vivo CD8-mediated cytotoxicity (83±3% vs 23±3%; p<0.001) but did not affect survival (10 days vs 14 days; p=ns). However, in CD4-deficient recipients, iNKTs were critical, since without CD4+ T cells and iNKTs, CD8-mediated in vivo cytotoxicity was completely abrogated (31±3% vs 2±1%; p<0.001) and HcTx survival was significantly prolonged (14 days vs 56 days; p<0.001). iNKTs enhanced the quantity of a novel CD8+ T cell subset, CD44+IFN-γ+CXCR3+CCR4+CD8+ T cells, in the liver (2-fold) in all HcTx recipients (p<0.03 for all comparisons). CXCR3+CCR4+CD8+ T cells, when compared to CXCR3+CCR4−CD8+ T cells, express higher IFN-γ (32±3% vs 9±1%; p<0.001) and TNF-α (37±3% vs 6±1%; p<0.001). They also exhibit greater in vivo cytotoxicity (13±1% vs 5±1%; p<0.001) and mediate rapid HcTx rejection in RAG1 KO recipients (5 days vs 16 days; p=0.02). We show that iNKTs enhance the expansion of highly cytotoxic CXCR3+CCR4+CD8+ T cells that mediate rapid rejection of HcTx.