Chronic alcohol use poses significant negative consequences to public health and, among its many biologic effects, is associated with significant T cell dysregulation within the adaptive immune ...system that has yet to be fully characterized. Novel, automated strategies for high dimensional flow cytometric analysis of the immune system are rapidly improving researchers' ability to detect and characterize rare cell types.
Using a murine model of chronic alcohol ingestion in conjunction with viSNE and CITRUS analysis tools, we performed a machine-driven, exploratory analysis comparing rare splenic subpopulations within the conventional CD4
, regulatory CD4
and CD8
T cell compartments between alcohol- and water-fed animals.
While there were no differences in the absolute numbers of bulk CD3
T cells, bulk CD4
T cells, bulk CD8
T cells, Foxp3
CD4
conventional T cells (T
) or Foxp3
CD4
regulatory T cells (T
), we identified populations of naïve Helios
CD4
T
and naïve CD103
CD8
splenic T cells that were decreased in chronically alcohol exposed mice versus water-fed controls. In addition, we identified increased CD69
Treg and decreased CD103
effector regulatory T cell (eT
) subsets in conjunction with increased frequency of a population that may represent a transitional phenotype between central regulatory T cell (cT
) and eT
.
These data provide further resolution into the character of decreased naïve T cell populations known to be present in alcohol exposed mice, as well as describe alterations in effector regulatory T cell phenotypes associated with the pathogenesis of chronic alcohol-induced immune dysfunction.
As the recognition that costimulatory signals are critical for optimal T-cell activation, proliferation, and differentiation, there has been an explosion in the study of costimulatory molecules and ...their roles in enhancing anti-donor T-cell responses following transplantation. Here, we focus on the bench-to-beside translation of blocking agents designed to target three critical costimulatory pathways: the CD28/CD80/CD86 pathway, the CD154/CD40 pathway, and the lymphocyte function associated antigen-1/intercellular adhesion molecule pathway. While blockade of each of these pathways proved promising in inhibiting donor-reactive T-cell responses and promoting long-term graft survival in murine models of transplantation, the progression of development of therapeutic agents to block these pathways has each taken a slightly different course. Both logistical and biological pitfalls have accompanied the translation of blockers of all three pathways into clinically applicable therapies, and the development of costimulatory blockade as a substitute for current standard-of-care calcineurin inhibitors has by no means reached completion. Collaboration between both the basic and clinical arenas will further propel the development of costimulation blockers currently in the pipeline, as well as of novel methods to target these critical pathways during transplantation.
Sepsis is a dysregulated systemic response to infection involving many inflammatory pathways and the induction of counter-regulatory anti-inflammatory processes that results in a state of immune ...incompetence and can lead to multi-organ failure. CXCR4 is a chemokine receptor that, following ligation by CXCL12, directs cells to bone marrow niches and also plays an important role in T cell cosignaling and formation of the immunological synapse. Here, we investigated the expression and function of CXCR4 in a murine model of polymicrobial sepsis. Results indicate that CXCR4 is selectively upregulated on naïve CD4+ and CD8+ T cells and CD4+ central memory T cells following the induction of sepsis, and that CXCR4 antagonism resulted in a significant decrease in sepsis-induced mortality. We probed the mechanistic basis for these findings and found that CXCR4 antagonism significantly increased the number of peripheral CD4+ and CD8+ T cells following sepsis. Moreover, mice treated with the CXCR4 antagonist contained fewer PD-1+ LAG-3+ 2B4+ cells, suggesting that blockade of CXCR4 mitigates CD4+ T cell exhaustion during sepsis. Taken together, these results characterize CXCR4 as an important pathway that modulates immune dysfunction and mortality following sepsis, which may hold promise as a target for future therapeutic intervention in septic patients.
Blockade of the CD40/CD154 pathway potently attenuates T-cell responses in models of autoimmunity, inflammation, and transplantation. Indeed, CD40 pathway blockade remains one of the most powerful ...methods of prolonging graft survival in models of transplantation. But despite this effectiveness, the cellular and molecular mechanisms underlying the protective effects of CD40 pathway blockade are incompletely understood. Furthermore, the relative contributions of deletion, anergy, and regulation have not been measured in a model in which donor-reactive CD4+ and CD8+ T-cell responses can be assessed simultaneously. To investigate the impact of CD40/CD154 pathway blockade on graft-specific T-cell responses, a transgenic mouse model was used in which recipients containing ovalbumin-specific CD4+ and CD8+ TCR transgenic T cells were grafted with skin expressing ovalbumin in the presence or absence of anti-CD154 and donor-specific transfusion. The results indicated that CD154 blockade altered the kinetics of donor-reactive CD8+ T-cell expansion, delaying differentiation into IFN-γ+ TNF+ multifunctional cytokine producers. The eventual differentiation of cytokine-producing effectors in tolerant animals coincided with the emergence of an antigen-specific CD4+ CD25hi Foxp3+ T-cell population, which did not arise from endogenous natural Treg but rather were peripherally generated from naïve Foxp3– precursors.
Micromanaging alloimmunity Ford, Mandy L
The Journal of clinical investigation,
07/2016, Volume:
126, Issue:
7
Journal Article
Peer reviewed
Open access
Increasing evidence indicates that microbes have a large influence on immune function. Previous studies have linked pathogenic microorganisms with decreased allograft tolerance and subsequent ...rejection. In this issue of the JCI, Lei and colleagues demonstrate that commensal organisms also influence the host response to allograft transplantation. Using murine skin and cardiac transplant models, the authors demonstrate that allograft rejection is accelerated in mice with a normal microbiome compared with germ-free animals and antibiotic-treated mice. The increased graft rejection observed in conventional animals was due to enhanced T cell priming and was mediated through type I IFN. Together, these results suggest that altering a patient's microbial community prior to transplant could improve allograft acceptance.
A hallmark of T cell dysregulation during sepsis is the downregulation of costimulatory molecules. CD28 is one of T cell costimulatory molecules significantly altered on memory T cells during sepsis. ...We recently showed that treatment with a αCD28 agonist in septic immunologically experienced mice led to improved survival. Therefore, here we aimed to identify the cell subset(s) necessary for the survival benefit observed in the context of CD28 agonism, and to further investigate the mechanism by which CD28 agonism improves sepsis survival in immunologically experienced mice. Methods: Mice received specific pathogen inoculation to generate memory T cell populations similar in frequency to that of adult humans. Once these infections were cleared and the T cell response had transitioned to the memory phase, animals were rendered septic via cecal ligation and puncture in the presence or absence of an agonistic anti-CD28 mAb.
Results demonstrated that CD8
T cells, and not bulk CD4
T cells or CD25
regulatory T cells, were necessary for the survival benefit observed in CD28 agonist-treated septic immunologically experienced mice. Upon examination of these CD8
T cells, we found that CD28 agonism in septic immunologically experienced mice was associated with an increase in Foxp3
CD8
T cells as compared to vehicle-treated controls. When CD8
T cells were depleted in septic immunologically experienced mice in the setting of CD28 agonism, a significant increase in levels of inflammatory cytokines in the blood was observed.
Taken together, these results indicate that CD28 agonism in immunologically experienced mice effectively suppresses inflammation via a CD8
-dependent mechanism to decrease mortality during sepsis.
T cell activation is a complex process that requires multiple cell signaling pathways, including a primary recognition signal and additional costimulatory signals. One of the best-characterized ...costimulatory pathways includes the Ig superfamily members CD28 and CTLA-4 and their ligands CD80 and CD86. Areas covered: This review discusses past, current and future biological therapies that have been utilized to block the CD28/CTLA-4 cosignaling pathway in the settings of autoimmunity and transplantation, as well the challenges facing successful implementation of these therapies. Expert opinion: The development of CD28 blockers Abatacept and Belatacept provided a more targeted therapy approach for transplant rejection and autoimmune disease relative to calcineurin inhibitors and anti-proliferatives, but overall efficacy may be limited due to their collateral effect of simultaneously blocking CTLA-4 coinhibitory signals. As such, current investigations into the potential of selective CD28 blockade to block the costimulatory potential of CD28 while exploiting the coinhibitory effects of CTLA-4 are promising. However, as selective CD28 blockade inhibits the activity of both effector and regulatory T cells, an important goal for the future is the design of therapies that will maximize the attenuation of effector responses while preserving the suppressive function of T regulatory cells.
Of (Dirty) Mice, Men and Memory Ford, Mandy L.
American journal of transplantation,
August 2016, 2016-Aug, 2016-08-00, 20160801, Volume:
16, Issue:
8
Journal Article
Peer reviewed
Open access
New data show that reported species‐specific differences between mouse and human immune profiles are the result of differential environmental exposures.
Kidney transplant recipients administered belatacept‐based maintenance immunosuppression present with a more favorable metabolic profile, reduced incidence of de novo donor‐specific antibodies ...(DSAs), and improved renal function and long‐term patient/graft survival relative to individuals receiving calcineurin inhibitor (CNI)‐based immunosuppression. However, the rates and severity of acute rejection (AR) are greater with the approved belatacept‐based regimen than with CNI‐based immunosuppression. Although these early co‐stimulation blockade‐resistant rejections are typically steroid sensitive, the higher rate of cellular AR has led many transplant centers to adopt immunosuppressive regimens that differ from the approved label. This article summarizes the available data on these alternative de novo belatacept‐based maintenance regimens. Steroid‐sparing, belatacept‐based immunosuppression (following T cell–depleting induction therapy) has been shown to yield AR rates comparable to those seen with CNI‐based regimens. Concomitant treatment with belatacept plus a mammalian target of rapamycin inhibitor (mTORi; sirolimus or everolimus) has yielded AR rates ranging from 0 to 4%. Because the optimal induction agent and number of induction doses; blood levels of mTORi; and dose, duration, and use of corticosteroids have yet to be determined, larger prospective clinical trials are needed to establish the optimal alternative belatacept‐based regimen for minimizing early cellular AR occurrence.
Kirk et al. discuss available data on alternative de novo belatacept‐based immunosuppression regimens in place of the approved belatacept regimen to reduce acute rejection rates in kidney transplant recipients.
Uremic cardiomyopathy, characterized by left ventricular hypertrophy, diastolic dysfunction, and impaired myocardial strain, contributes to increased cardiovascular mortality in patients with CKD. ...Emerging evidence suggests a pathogenic role for T cells during chronic heart failure.
To determine whether T cells contribute to uremic cardiomyopathy pathogenesis, we modeled this condition by inducing CKD
5/6th nephrectomy in mice. We used flow cytometry to assess expression of markers of T cell memory or activation by lymphocytes from CKD mice and controls, as well as lymphocyte capacity for cytokine production. Flow cytometry was also used to quantify immune cells isolated from heart tissue. To test effects of T cell depletion on cardiac function, we gave CKD mice anti-CD3 antibody injections to deplete T cells and compared heart function (assessed by echocardiography) with that of controls. Finally, we correlated T cell phenotypes with structural and functional measures on clinically acquired echocardiograms in children with CKD.
Mice with CKD accumulated T cells bearing markers of memory differentiation (CD44
) and activation (PD-1, KLRG1, OX40), as reported previously in human CKD. In addition, mice with CKD showed T cells infiltrating the heart. T cell depletion significantly improved both diastolic function and myocardial strain in CKD mice without altering hypertension or degree of renal dysfunction. In children with CKD, increasing frequency of T cells bearing activation markers PD-1 and/or CD57 was associated with worsening diastolic function on echocardiogram.
CKD results in an accumulation of proinflammatory T cells that appears to contribute to myocardial dysfunction.
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