Background. We previously reported the novel activity of alloprimed CD8+ T cells that suppress posttransplant alloantibody production. The purpose of the study is to investigate the expression and role of CXCR5 on antibody-suppressor CD8+ T-cell function. Methods. C57BL/6 mice were transplanted with FVB/N hepatocytes. Alloprimed CD8+ T cells were retrieved on day 7 from hepatocyte transplant recipients. Unsorted or flow-sorted (CXCR5+CXCR3− and CXCR3+CXCR5−) alloprimed CD8+ T-cell subsets were analyzed for in vitro cytotoxicity and capacity to inhibit in vivo alloantibody production following adoptive transfer into C57BL/6 or high alloantibody-producing CD8 knock out (KO) hepatocyte transplant recipients. Alloantibody titer was assessed in CD8 KO mice reconstituted with naive CD8+ T cells retrieved from C57BL/6, CXCR5 KO, or CXCR3 KO mice. Antibody suppression by ovalbumin (OVA)-primed monoclonal OVA-specific t-cell receptor transgenic CD8+ T cells (OT-I) CXCR5+ or CXCR3+ CD8+ T-cell subsets was also investigated. Results. Alloprimed CXCR5+CXCR3−CD8+ T cells mediated in vitro cytotoxicity of alloprimed “self” B cells, while CXCR3+CXCR5−CD8+ T cells did not. Only flow-sorted alloprimed CXCR5+CXCR3−CD8+ T cells (not flow-sorted alloprimed CXCR3+CXCR5−CD8+ T cells) suppressed alloantibody production and enhanced graft survival when transferred into transplant recipients. Unlike CD8+ T cells from wild-type or CXCR3 KO mice, CD8+ T cells from CXCR5 KO mice do not develop alloantibody-suppressor function. Similarly, only flow-sorted CXCR5+CXCR3− (and not CXCR3+CXCR5−) OVA-primed OT-I CD8+ T cells mediated in vivo suppression of anti-OVA antibody production. Conclusions. These data support the conclusion that expression of CXCR5 by antigen-primed CD8+ T cells is critical for the function of antibody-suppressor CD8+ T cells.

CCR5 KO kidney transplant (KTx) recipients are extraordinarily high alloantibody producers and develop pathology that mimics human antibody‐mediated rejection (AMR). C57BL/6 and CCR5 KO mice (H‐2b) were transplanted with A/J kidneys (H‐2a); select cohorts received adoptive cell therapy (ACT) with alloprimed CXCR5+CD8+ T cells (or control cells) on day 5 after KTx. ACT efficacy was evaluated by measuring posttransplant alloantibody, pathology, and allograft survival. Recipients were assessed for the quantity of CXCR5+CD8+ T cells and CD8‐mediated cytotoxicity to alloprimed IgG+ B cells. Alloantibody titer in CCR5 KO recipients was four‐fold higher than in C57BL/6 recipients. The proportion of alloprimed CXCR5+CD8+ T cells 7 days after KTx in peripheral blood, lymph node, and spleen was substantially lower in CCR5 KO compared to C57BL/6 recipients. In vivo cytotoxicity towards alloprimed IgG+ B cells was also reduced six‐fold in CCR5 KO recipients. ACT with alloprimed CXCR5+CD8+ T cells (but not alloprimed CXCR5−CD8+ or third‐party primed CXCR5+CD8+ T cells) substantially reduced alloantibody titer, ameliorated AMR pathology, and prolonged allograft survival. These results indicate that a deficiency in quantity and function of alloprimed CXCR5+CD8+ T cells contributes to high alloantibody and AMR in CCR5 KO recipient mice, which can be rescued with ACT.

Background:We recently reported that a novel CXCR5 + IFN-γ + CD8 + T cell subset significantly inhibits posttransplant alloantibody production in a murine transplant model. These findings prompted the current study to investigate the association of human CD8 + T cells with the same phenotype with the development of de novo donor-specific antibody (DSA) after kidney transplantation. Methods:In the current studies, we prospectively and serially analyzed peripheral blood CD8 + and CD4 + T cell subsets and monitored for the development of de novo DSA in kidney transplant recipients during the first year posttransplant. We report results on 95 first-time human kidney transplant recipients with 1-year follow-up.

CD8+ T cells have conventionally been studied in relationship to pathogen or tumor clearance. Recent reports have identified novel functions of CXCR5+CD8+ T cells that can home to lymphoid follicles, a key site of Ab production. In this review, we provide an in-depth analysis of conflicting reports regarding the impact of CXCR5+CD8+ T cells on Ab production and examine the data supporting a role for Ab enhancement (B cell helper) and Ab downregulation (Ab-suppressor) by CXCR5+CD8+ T cell subsets. CXCR5+CD8+ T cell molecular phenotypes are associated with CD8-mediated effector functions, including distinct subsets that regulate Ab responses. Coinhibitory molecule PD-1, among others, distinguishes CXCR5+CD8+ T cell subsets. We also provide, to our knowledge, the first in-depth review of human CXCR5+CD8+ T cells in the context of clinical outcomes and discuss the potential utility of monitoring the quantity of peripheral blood or tissue infiltrating CXCR5+CD8+ T cells as a prognostic tool in multiple disease states.

Background The liver immune environment is tightly regulated to balance immune activation with immune tolerance. Understanding the dominant immune pathways initiated in the liver is important since the liver is a site for cell transplantation, such as for islet and hepatocyte transplantation. The purpose of this study is to examine the consequences of alloimmune stimulation when allogeneic cells are transplanted to the liver in comparison to a different immune locale, such as the kidney. Methods We investigated cellular and humoral immune responses when allogeneic hepatocytes are transplanted directly to the recipient liver by intraportal injection. A heterotopic kidney engraftment site was used for comparison to immune activation in the liver microenvironment. Results Transplantation of allogeneic hepatocytes delivered directly to the liver, via recipient portal circulation, stimulated long-term, high magnitude CD8+ T cell-mediated allocytotoxicity. CD8+ T cells initiated significant in vivo allocytotoxicity as well as rapid rejection of hepatocytes transplanted to the liver even in the absence of secondary lymph nodes or CD4+ T cells. In contrast, in the absence of recipient peripheral lymphoid tissue and CD4+ T cells, CD8-mediated in vivo allocytotoxicity was abrogated and rejection was delayed when hepatocellular allografts were transplanted to the kidney subcapsular site. Conclusions These results highlight the CD8-dominant proinflammatory immune responses unique to the liver microenvironment. Allogeneic cells transplanted directly to the liver do not enjoy immune privilege but rather require immunosuppression to prevent rejection by a robust and persistent CD8‐dependent allocytotoxicity primed in the liver.