Hepatocyte transplantation (HcTx) is a potential therapeutic modality for patients with liver disease. Despite examples of antigen acceptance in the liver, allogeneic HcTx into patients exhibits significant, but short-lived, benefits with immunogenicity remaining a barrier to allograft survival. In our well-characterized animal model, Hc allografts are highly immunogenic and stimulate multiple rejection mechanisms including: antibody-mediated rejection, CD4-dependent CD8-mediated rejection, and CD4-independent CD8-mediated rejection. Our published reports and new data suggest that type I NKT cells (iNKTs) are critical to the development of each rejection pathway. We first reported that alloantibody titer following HcTx is critically inhibited (~10-100 fold) in the absence of iNKTs (Ja18 KO recipients). To further investigate the effects of iNKTs on humoral as well as cellular alloimmunity, we utilized immunohistochemistry (IHC), flow cytometry, in vivo cytotoxicity assays, and analysis of allograft survival following HcTx. Ja18 KO recipients exhibited significantly reduced germinal center size (GL-7 staining by IHC; day 14 postTx) and number of splenic IL-4⁺ and IL-21⁺CD4⁺ T_FH cells [day 7; wild-type (WT): IL-4=100±4×10³, IL-21=145±5×10³ vs. Ja18 KO: IL-4=25±3×10³, IL-21=75±14×10³ cells/spleen; p<0.04] by flow cytometry compared to WT recipients. Additionally, CD4-dependent CD8⁺ T cell-mediated cytotoxicity to allogeneic targets (day 7; 89.8±2.6%) was reduced by ~70% in Ja18 KO recipients (26.9±3.3%, p<0.001). When iNKT cells are adoptively transferred (AT) into Ja18 KO recipients (same day as Tx), CD4-dependent CD8⁺ T cell-mediated cytotoxicity was significantly enhanced (35.3±4.6%; p=0.01). Interestingly, CD4-independent, CD8⁺ T cell-mediated cytotoxicity (26.9±5.1%) was abrogated in CD4-depleted Ja18 KO recipients (2.0±.0.9%; p=0.009) and allogeneic HcTx exhibited prolonged survival in CD4-depleted Ja18 KO recipients (MST>day 30 vs. day 14 rejection in CD4-depleted WT recipients; p=0.03). When iNKT cells are AT into CD4-depleted Ja18 KO recipients, CD4-independent CD8⁺ T cell-mediated cytotoxicity was significantly enhanced (6.0±0.8; p=0.001) and kinetics of allograft rejection were accelerated (MST=day 14; p=0.03). These data support the hypothesis that iNKTs are central to the humoral- and cellular-mediated response following HcTx and targeting iNKTs for immunosuppression may lead to enhanced graft survival.

CITATION INFORMATION: Elzein S., Zimmerer J., Ringwald B., Avila C., Bumgardner G. Type I NKT Cells Augment Humoral and Cellular Alloimmunity in Response to Hepatocyte Transplantation Am J Transplant. 2017;17 (suppl 3).

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