Antibody-Suppressor CXCR5+CD8+ T Cells Are More Potent Regulators of Humoral Alloimmunity after Kidney Transplant in Mice Compared to CD4+ Regulatory T Cells.

Adoptive cell therapy (ACT), especially with CD4+ regulatory T cells (CD4+ Tregs), is an emerging therapeutic strategy to minimize immunosuppression and promote long-term allograft acceptance, although much research remains to realize its potential. In this study, we investigated the potency of novel Ab-suppressor CXCR5+CD8+ T cells (CD8+ TAb-supp) in comparison with conventional CD25highFoxp3+CD4+ Tregs for suppression of humoral alloimmunity in a murine kidney transplant (KTx) model of Ab-mediated rejection (AMR). We examined quantity of peripheral blood, splenic and graft-infiltrating CD8+ TAb-supp, and CD4+ Tregs in KTx recipients and found that high alloantibody-producing CCR5 knockout KTx recipients have significantly fewer post-transplant peripheral blood and splenic CD8+ TAb-supp, as well as fewer splenic and graft-infiltrating CD4+ Tregs compared with wild-type KTx recipients. ACT with alloprimed CXCR5+CD8+ T cells reduced alloantibody titer, splenic alloprimed germinal center (GC) B cell quantity, and improved AMR histology in CCR5 knockout KTx recipients. ACT with alloprimed CD4+ Treg cells improved AMR histology without significantly inhibiting alloantibody production or the quantity of splenic alloprimed GC B cells. Studies with TCR transgenic mice confirmed Ag specificity of CD8+ TAb-supp-mediated effector function. In wild-type recipients, CD8 depletion significantly increased alloantibody titer, GC B cells, and severity of AMR pathology compared with isotype-treated controls. Anti-CD25 mAb treatment also resulted in increased but less pronounced effect on alloantibody titer, quantity of GC B cells, and AMR pathology than CD8 depletion. To our knowledge, this is the first report that CD8+ TAb-supp cells are more potent regulators of humoral alloimmunity than CD4+ Treg cells.

Roadmap for Research and Scholarship in General Surgery Residency Training: Report of The Research Subcommittee of Blue Ribbon Committee II on Surgical Education and Training.

OBJECTIVE: To review the current state of research training during surgical residency and make recommendations commensurate with current surgical training and academic environment. SUMMARY BACKGROUND DATA: Research training has been a mainstay of academic surgical programs, yet the scientific disciplines have evolved significantly from the traditional years of bench research. It is time to reconsider how research training should prepare surgeons for future academic practice and ensure the foundational knowledge of research evidence. METHODS: As part of the Blue Ribbon Committee II, a research subcommittee was tasked to make recommendations on research training during surgical residency. Our eight-member panel brought diverse perspectives of the roles and goals of research training. We also sought input from a convenience sample of current and recent surgical residents on impact of research training during their residency. RESULTS: We identified a lack of a common framework and foundational research training for all surgical residents. Participation in dedicated years of scholarly activity helped trainees meet several professional and personal goals. The lack of an integrated, dedicated research track may dissuade some medical school graduates from pursuing surgery. CONCLUSIONS: We recommend incorporating a minimum standard for all trainees and flexibility in dedicated scholarly training to meet the needs of future academic surgeons.

CXCR5+CD8+ T cells: A Review of their Antibody Regulatory Functions and Clinical Correlations.

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 antibody production. In this review we provide an in-depth analysis of conflicting reports regarding the impact of CXCR5+CD8+ T cells on antibody production and examine the data supporting a role for antibody-enhancement (B cell "helper") and antibody-downregulation (antibody-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 antibody responses. Co-inhibitory molecule PD-1, among others, distinguish CXCR5+CD8+ T cell subsets. We also provide 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.

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

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.

Antibody-suppressor CXCR5+ CD8+ T cellular therapy ameliorates antibody-mediated rejection following kidney transplant in CCR5 KO mice.

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.

Facilitating Success of the Early Stage Surgeon Scientist Trainee: Growing the Surgeon Scientist Pipeline.

OBJECTIVE: Surgeon scientists bring to bear highly specialized talent and innovative and impactful solutions for complicated clinical problems. Our objective is to inform and provide framework for early stage surgeon scientist training and support. SUMMARY OF BACKGROUND DATA: Undergraduate, medical student, and residency experiences impact the career trajectory of surgeon scientists. To combat the attrition of the surgeon scientist pipeline, interventions are needed to engage trainees and to increase the likelihood of success of future surgeon scientists. METHODS: A surgery resident writing group at an academic medical center, with guidance from faculty, prepared this guidance document for early stage surgeon scientist trainees with integration of the published literature to provide context. The publicly available National Institutes of Health RePORTER tool was queried to provide data salient to early stage surgeon scientist training. RESULTS: The educational path of surgeons and the potential research career entry points are outlined. Challenges and critical supportive elements needed to inspire and sustain progress along the surgeon scientist training path are detailed. Funding mechanisms available to support formal scientific training of early stage surgeon scientists are identified and obstacles specific to surgical careers are discussed. CONCLUSIONS: This guidance enhances awareness of essential education, communication, infrastructure, resources, and advocacy by surgery leaders and other stakeholders to promote quality research training in residency and to re-invigorate the surgeon scientist pipeline.

Thoracic transplantation during the COVID-19 pandemic.

The worldwide pandemic caused by COVID-19, resulting from the infection by betacoronarvirus SARS-CoV-2, has dramatically altered healthcare worldwide. Due to the highly contagious nature of SARS-CoV2, coupled with hospitals and intensive care units being overwhelmed, numerous transplant programs either slowed or shut down completely. While there have been isolated reports of COVID-19 in transplant recipients, no study to date has examined how COVID-19 affected actual transplant patterns and outcomes in the United States. Of particular importance is the impact of COVID-19 on mortality in waitlisted patients and transplant recipients. Using the Scientific Registry of Transplant Recipients (SRTR) dataset, we compared waitlist and transplant characteristics from 3/2019-8/2019 to 3/2020-8/2020, as well as COVID-19 associated mortality in patients with prior heart or lung transplant or those active on the waitlist. Overall, there was an initial decrease in transplant volume in April 2020; however, volumes have normalized since then, with comparable outcomes to similar calendar months in 2019. Additionally, there were no significant changes in post-transplant outcomes or waiting list mortality. Given the ongoing COVID-19 pandemic, it would be beneficial to maintain current practices for thoracic transplantation, to continue to provide this life-saving therapy to those in need.

Obesity, transplantation, and bariatric surgery: An evolving solution for a growing epidemic.

The increasing obesity epidemic has major implications in the realm of transplantation. Patients with obesity face barriers in access to transplant and unique challenges in perioperative and postoperative outcomes. Because of comorbidities associated with obesity, along with the underlying end-stage organ disease leading to transplant candidacy, these patients may not even be referred for transplant evaluation, much less be waitlisted or actually undergo transplant. However, the use of bariatric surgery in this population can help optimize the transplant candidacy of patients with obesity and end-stage organ disease and improve perioperative and postoperative outcomes. We review the impact of obesity on kidney, liver, and cardiothoracic transplant candidates and recipients and explore potential interventions to address obesity in these populations.

The impact of donor and recipient diabetes on renal transplant outcomes.

The use of diabetic kidneys is increasing worldwide with better outcome than being on waitlist and possible reversal of diabetic changes in transplanted kidneys. But particular caution is warranted in diabetic donor-recipient combination. Total 1223 deceased donor kidney transplants were performed at our center between 2008 and 2018. 689 from non-diabetic donor (NDD) to non-diabetic recipient, 400 from non-diabetic donor to diabetic recipient, 97 from diabetic to non-diabetic recipient, and 32 from diabetic donor (DD) to diabetic recipient. The DD was older than NDDs (median age 48 vs 39 years, P < 0.0001). DD had higher BMI (35.6 vs 26.9, P < 0.0001), higher KDPI (74% vs 37%, P < 0.0001), and higher terminal creatinine (1.10 mg/dl vs 0.95 mg/dl, p 0.0046) than the NDD. Diabetes recipients were comparatively older (57 vs 54, P < 0.001). DD recipients had higher serum creatinine at 6 months (1.70 vs 1.50 mg/dl, p 0.00304) and 2 years post-transplant (1.70 vs 1.50 mg/dl P < 0.0002). DD recipients had more favorable end CPRA than NDD recipients (77.5% at 0% vs 67.4% at 0, P = 0.0074). Ten-year patient and graft survival was best in NDD-recipient pair and worse in DD-recipient pair. Diabetic donor kidneys to diabetic recipients have lower 1-, 3-, and 5-year graft survival.

"Early" and "Late" Hospital readmissions in the first year after kidney transplant at a single center.

BACKGROUND: Hospital readmission (HR) after surgery is considered a quality metric. METHODS: Data on 2371 first-time adult kidney transplant (KT) recipients were collected to analyze the "early" (≤30 days) and "late" (31-365 days) HR patterns after KT at a single center over a 12-year time span (2002-2013). RESULTS: 30-day, 90-day, and 1-year HR were 31%, 41%, and 53%, respectively. Risk factors for HR included age >50, female sex, black race, BMI >30, transplant LOS >5 days, and pre-transplant time on dialysis >765 days. Indications for early (n = 749) and late (n = 508) HR were similar. Early HR (OR: 3.80, P = .007) and black race (OR: 2.38, P = .009) were associated with higher odds of 1-year graft failure while frequency (1-2, 3-4, 5+) of HR (ORs: 4.68, 8.36, 9.44, P < .001) and age > 50 (OR: 2.11, P = .007) were associated with higher odds of 1-year mortality. Transplant LOS > 5 days increased both odds of 1-year graft failure (OR: 3.51, P = .001) and mortality (OR: 2.05, P = .006). One-year graft and recipient survival were 96.7% and 94.8%, respectively. CONCLUSIONS: Hospital readmission was associated with reduced graft and patient survival; however, despite a relatively high and consistent HR rate after KT, overall 1-year graft and patient survival was high.

Critical Role of Macrophage FcγR Signaling and Reactive Oxygen Species in Alloantibody-Mediated Hepatocyte Rejection.

Humoral alloimmunity negatively impacts both short- and long-term cell and solid organ transplant survival. We previously reported that alloantibody-mediated rejection of transplanted hepatocytes is critically dependent on host macrophages. However, the effector mechanism(s) of macrophage-mediated injury to allogeneic liver parenchymal cells is not known. We hypothesized that macrophage-mediated destruction of allogeneic hepatocytes occurs by cell-cell interactions requiring FcγRs. To examine this, alloantibody-dependent hepatocyte rejection in CD8-depleted wild-type (WT) and Fcγ-chain knockout (KO; lacking all functional FcγR) transplant recipients was evaluated. Alloantibody-mediated hepatocellular allograft rejection was abrogated in recipients lacking FcγR compared with WT recipients. We also investigated anti-FcγRI mAb, anti-FcγRIII mAb, and inhibitors of intracellular signaling (to block phagocytosis, cytokines, and reactive oxygen species [ROS]) in an in vitro alloantibody-dependent, macrophage-mediated hepatocytoxicity assay. Results showed that in vitro alloantibody-dependent, macrophage-mediated hepatocytotoxicity was critically dependent on FcγRs and ROS. The adoptive transfer of WT macrophages into CD8-depleted FcγR-deficient recipients was sufficient to induce alloantibody-mediated rejection, whereas adoptive transfer of macrophages from Fcγ-chain KO mice or ROS-deficient (p47 KO) macrophages was not. These results provide the first evidence, to our knowledge, that alloantibody-dependent hepatocellular allograft rejection is mediated by host macrophages through FcγR signaling and ROS cytotoxic effector mechanisms. These results support the investigation of novel immunotherapeutic strategies targeting macrophages, FcγRs, and/or downstream molecules, including ROS, to inhibit humoral immune damage of transplanted hepatocytes and perhaps other cell and solid organ transplants.

Early immunosuppression treatment correlates with later de novo donor-specific antibody development after kidney and pancreas transplantation.

BACKGROUND: De novo donor-specific antibodies (dnDSA) post-transplant correlate with a higher risk of immunologic graft injury and loss following kidney and pancreas transplantation. Post-transplant dnDSA can occur within the first post-transplant year. METHODS: In this study, 817 of 1290 kidney and simultaneous kidney/pancreas recipients were tested for dnDSA post-transplant. Recipient immunosuppressive treatment at one, three, six, and 12 months post-transplant was correlated with dnDSA incidence by univariate and multivariate analyses. RESULTS: The overall incidence of dnDSA was 21.3% detected a median of 3.5 yr post-transplant. By univariate analysis, the immunosuppressive treatment at all time points correlated with dnDSA (p < 0.01). Month 6 treatment correlated best in multivariable analysis (p = 0.004). At six months, recipients receiving rapamune/mycophenolic acid (Rapa/MPA) had the highest dnDSA incidence at five yr (25.3%) and last follow-up (30.7%), those treated with cyclosporine/rapamune (CNI/Rapa) had the lowest incidence at five yr (10.8%) and last follow-up (18.6%), and cyclosporine/mycophenolic acid (CNI/MPA) treatment had an intermediate incidence at five yr (16.7%) and last follow-up (20.4%) (p < 0.01). Six-month CNI/MPA and Rapa/MPA treatment significantly correlated with dnDSA (hazard ratios of 2.36 and 1.80, respectively) by Cox proportional hazards regression modeling. CONCLUSION: The risk of post-transplant dnDSA development correlates with early immunosuppressive management.

CXCR5 + CD8 + T Cell-mediated Suppression of Humoral Alloimmunity and AMR in Mice Is Optimized With mTOR and Impaired With Calcineurin Inhibition.

BACKGROUND: Adoptive cellular therapy (ACT) with antibody-suppressor CXCR5 + CD8 + T cells (CD8 + T Ab-supp ) inhibits alloantibody production, antibody-mediated rejection (AMR), and prolongs graft survival in multiple transplant mouse models. However, it is not known how conventional immunosuppressive agents impact the efficacy of CD8 + T Ab-supp ACT. METHODS: We investigated the efficacy of CD8 + T Ab-supp cell ACT when combined with calcineurin inhibitor (CNi) or mammalian target of rapamycin inhibitor (mTORi) in a murine model of kidney transplant. RESULTS: ACT-mediated decrease in germinal center B cells, posttransplant alloantibody titer, and amelioration of AMR in high alloantibody-producing CCR5 knockout kidney transplant recipients were impaired when ACT was combined with CNi and enhanced when combined with mTORi. CNi (but not mTORi) reduced ACT-mediated in vivo cytotoxicity of IgG + B cells and was associated with increased quantity of germinal center B cells. Neither CNi nor mTORi treatment impacted the expression of cytotoxic effector molecules (FasL, Lamp1, perforin, granzyme B) by CD8 + T Ab-supp after ACT. Concurrent treatment with CNi (but not mTORi) reduced in vivo proliferation of CD8 + T Ab-supp after ACT. The increase in quantity of splenic CD44 + CXCR5 + CD8 + T cells that occurs after ACT was reduced by concurrent treatment with CNi but not by concurrent treatment with mTORi (dose-dependent). CONCLUSIONS: Impaired efficacy of ACT by CNi is attributed to reduced persistence and/or expansion of CD8 + T Ab-supp cells after ACT. In contrast, concurrent immunosuppression with mTORi preserves CD8 + T Ab-supp cells quantity, in vivo proliferation, and in vivo cytotoxic effector function after ACT and enhances suppression of humoral alloimmunity and AMR.

CD8+ T cells negatively regulate IL-4-dependent, IgG1-dominant posttransplant alloantibody production.

We have previously reported that CD8(+) T cells significantly influence Ab production based on the observation that posttransplant alloantibody levels in CD8-deficient murine hepatocyte transplant recipients are markedly enhanced. However, the precise mechanisms contributing to enhanced alloantibody production in the absence of CD8(+) T cells is not understood. We hypothesized that alloactivated CD8(+) T cells inhibit Ab production by skewing toward a proinflammatory cytokine profile, whereas when these cells are absent, an anti-inflammatory cytokine profile shifts the alloimmune response toward alloantibody production. To investigate this possibility, alloantibody isotype profiles were examined in CD8-deficient and wild-type hepatocyte recipients. We found that IgG1 (IL-4-dependent isotype) was the dominant alloantibody isotype in wild-type recipients as well as in CD8-deficient recipients, although the amount of alloantibody in the latter group was substantially higher. Utilizing real-time PCR we found that CD4(+) T cells from wild-type recipients significantly upregulated IFN-γ but not IL-4 mRNA. In contrast, in the absence of CD8(+) T cells, CD4(+) T cells switched to significantly upregulate IL-4 mRNA, while IFN-γ was downregulated. IL-4 knockout mice do not produce any posttransplant alloantibody. However, adoptive transfer of wild-type CD4(+) T cells into CD8-depleted IL-4 knockout mice restores high alloantibody levels observed in CD8-depleted wild-type recipients. This suggests that IL-4-producing CD4(+) T cells are critical for posttransplant alloantibody production. Additionally, this CD8-mediated regulation of posttransplant alloantibody production is IFN-γ-dependent. Further elucidation of the mechanisms by which CD8(+) T cells influence Ab production will significantly contribute to development of therapies to manipulate humoral responses to Ag.

Machine perfusion of kidney allografts affects early but not late graft function.

BACKGROUND: Hypothermic machine perfusion (HMP) parameters are influenced by donor variables which further affect recipient outcome. Interplay between these parameters can help to predict kidney performance on pump and the long term outcome. METHODS: All the kidneys transplanted at our center between May 2013 through November 2017 were included in the study. Donor and recipient data was obtained from internal database. Multiple logistic regression models with backward selection were used to determine significant donor and pump variables. RESULTS: Donor BMI, KDPI, age and donor sex had a significant association with pump flow. Donor sex, donor type, KDPI and age had significant effect on RI. Diastolic pressure and KDPI were significantly associated with DGF. Duration on pump, KDPI, flow, donor creatinine and type of donor were significantly associated with day 5 creatinine. KDPI was significantly associated with Day 365 creatinine. CONCLUSION: HMP effects early graft function while the long term function depends on donor parameters.

Spinal Stroke following Kidney Transplant.

Complications are a part of surgery. Spinal infarctions are a dreaded complication of aortic surgery. We present a patient who developed a spinal infarct after a kidney transplant. We were unable to find a causative factor in our search for etiology. In our review of the literature, we were unable to find a similar report. We present this case report to highlight a rare complication of kidney transplantation and to reinforce that patients requiring kidney transplant are complex patients with multiple comorbidities that can cause a multitude of complications in the periop period.

Critical role of effector macrophages in mediating CD4-dependent alloimmune injury of transplanted liver parenchymal cells.

Despite the recognition that humoral rejection is an important cause of allograft injury, the mechanism of Ab-mediated injury to allograft parenchyma is not well understood. We used a well-characterized murine hepatocellular allograft model to determine the mechanism of Ab-mediated destruction of transplanted liver parenchymal cells. In this model, allogeneic hepatocytes are transplanted into CD8-deficient hosts to focus on CD4-dependent, alloantibody-mediated rejection. Host serum alloantibody levels correlated with in vivo allospecific cytotoxic activity in CD8 knockout hepatocyte rejector mice. Host macrophage depletion, but not CD4(+) T cell, NK cell, neutrophil, or complement depletion, inhibited in vivo allocytotoxicity. Recipient macrophage deficiency delayed CD4-dependent hepatocyte rejection and inhibited in vivo allocytotoxicity without influencing alloantibody production. Furthermore, hepatocyte coincubation with alloantibody and macrophages resulted in Ab-dependent hepatocellular cytotoxicity in vitro. These studies are consistent with a paradigm of acute humoral rejection in which CD4(+) T cell-dependent alloantibody production results in the targeting of transplanted allogeneic parenchymal cells for macrophage-mediated cytotoxic immune damage. Consequently, strategies to eliminate recipient macrophages during CD4-dependent rejection pathway may prolong allograft survival.

Inverse Association Between the Quantity of Human Peripheral Blood CXCR5+IFN-γ+CD8+ T Cells With De Novo DSA Production in the First Year After Kidney Transplant.

BACKGROUND: We recently reported that a novel CXCR5IFN-γCD8 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. RESULTS: Twenty-three recipients (24.2%) developed de novo DSA within 1-year posttransplant. Recipients who developed DSA had significantly lower quantities of peripheral CXCR5IFN-γCD8 T cells (P = 0.01) and significantly lower ratios of CXCR5IFN-γCD8 T cell to combined CD4 Th1/Th2 cell subsets (IFN-γCD4 and IL-4CD4 cells; P = 0.0001) compared to recipients who remained DSA-negative over the first-year posttransplant. CONCLUSIONS: Our data raise the possibility that human CXCR5IFN-γCD8 T cells are a homolog to murine CXCR5IFN-γCD8 T cells (termed antibody-suppressor CD8 T cells) and that the quantity of CXCR5IFN-γCD8 T cells (or the ratio of CXCR5IFN-γCD8 T cells to Th1/Th2 CD4 T cells) may identify recipients at risk for development of DSA.

Antibody-suppressor CD8+ T Cells Require CXCR5.

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 (CXCR5CXCR3 and CXCR3CXCR5) 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 CXCR5CXCR3CD8 T cells mediated in vitro cytotoxicity of alloprimed "self" B cells, while CXCR3CXCR5CD8 T cells did not. Only flow-sorted alloprimed CXCR5CXCR3CD8 T cells (not flow-sorted alloprimed CXCR3CXCR5CD8 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 CXCR5CXCR3 (and not CXCR3CXCR5) 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.