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Background-The role of adaptive immunity, especially CD4ϩ T-helper cells, has not yet been systematically investigated in wound healing and remodeling after myocardial infarction (MI). Therefore, we studied whether CD4 ϩ T cells become activated and influence wound healing after experimental MI in mice. Methods and Results-When we compared sham versus MI in wild-type (WT) mice, T-cell receptor-dependent activation of both conventional Foxp3 Ϫ and regulatory Foxp3 ϩ CD4 ϩ T cells could be demonstrated in heart-draining lymph nodes within the first week after MI. Concomitantly, we found infiltration of CD4 ϩ T cells in infarcted myocardium. To study the role of CD4 ϩ T cells in wound healing and remodeling, CD4 ϩ T-cell-deficient mice (CD4 knockout [KO], MHCII ⌬/⌬ ) and T-cell receptor-transgenic OT-II mice recognizing an irrelevant ovalbumin-derived peptide were studied. Serial echocardiography up to day 56 after MI revealed increased left ventricular dilation in CD4 KO compared with WT mice. Within the infarcted myocardium, CD4 KO mice displayed higher total numbers of leukocytes and proinflammatory monocytes (18.3Ϯ3.0 10

Nonalcoholic fatty liver disease is increasing in prevalence. It can be subdivided into nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). Five to twenty percent of cases progress from NAFL to NASH. Increased hepatic Th17 cells and IL-17 expression were observed in NASH mice and patients, respectively. We analyzed CD4+ effector T cells and regulatory T cells (Tregs) from peripheral blood and livers of NAFL and NASH patients. A total of 51 NAFL patients, 30 NASH patients, 31 nonalcoholic fatty liver disease patients (without histology), and 43 healthy controls were included. FACS analysis was performed on PBMCs and intrahepatic lymphocytes. Compared with healthy controls, a lower frequency of resting Tregs (rTregs; CD4+CD45RA+CD25++) and higher frequencies of IFN-γ+ and/or IL-4+ cells were detected among CD4+ T cells of peripheral blood in NASH, and to a lesser degree in NAFL. In hepatic tissue, NAFL to NASH progression was marked by an increase in IL-17+ cells among intrahepatic CD4+ T cells. To define immunological parameters in peripheral blood to distinguish NAFL from NASH, we calculated different ratios. Th17/rTreg and Th2/rTreg ratios were significantly increased in NASH versus NAFL. The relevance of our findings for NASH pathogenesis was highlighted by the normalization of all of the changes 1 y after bariatric surgery. In conclusion, our data indicate that NAFL patients show changes in their immune cell profile compared with healthy controls. NAFL to NASH progression is marked by an increased frequency of IL-17+ cells among intrahepatic CD4+ T cells and higher Th17/rTreg and Th2/rTreg ratios in peripheral blood.

Changes in cytoplasmic Ca 2+ levels regulate a variety of fundamental cellular functions in virtually all cells. In nonexcitable cells, a major pathway of Ca 2+ entry involves receptor-mediated depletion of intracellular Ca 2+ stores followed by the activation of store-operated calcium channels in the plasma membrane. We have established a mouse line expressing an activating EF hand motif mutant of stromal interaction molecule 1 (Stim1), an ER receptor recently identified as the Ca 2+ sensor responsible for activation of Ca 2+ releaseactivated (CRAC) channels in T cells, whose function in mammalian physiology is not well understood. Mice expressing mutant Stim1 had macrothrombocytopenia and an associated bleeding disorder. Basal intracellular Ca 2+ levels were increased in platelets, which resulted in a preactivation state, a selective unresponsiveness to immunoreceptor tyrosine activation motif-coupled agonists, and increased platelet consumption. In contrast, basal Ca 2+ levels, but not receptor-mediated responses, were affected in mutant T cells. These findings identify Stim1 as a central regulator of platelet function and suggest a cell type-specific activation or composition of the CRAC complex. IntroductionThe regulation of intracellular Ca 2+ ([Ca 2+ ] i ) is essentially involved in signaling processes in virtually all cells. In nonexcitable cells, including hematopoietic cells, Ca 2+ is released from the ER via inositol 1,4,5-triphosphate-mediated (IP 3 -mediated) receptor activation triggered by ligand-activated plasma membrane receptors. If the limited Ca 2+ reservoir of the ER becomes exhausted, extracellular Ca 2+ enters the cytoplasm by a mechanism known as store-operated Ca 2+ entry (SOCE) (1, 2). Although electrophysiologically well defined for more than a decade, the molecular identity of the pivotal proteins undoubtedly involved in SOCE has been discovered only recently. Stromal interaction molecule 1 (Stim1) is an ER resident protein necessary for the detection of ER Ca 2+ depletion (3-6). The 4-transmembrane domain protein Orai1, or CRACM, was reported recently to confer SOC activity (4,(7)(8)(9)(10)(11)(12). In T cells, Orai1 appears to be the predominant SOC (9), despite the fact that the C-terminal region of Stim1 has been shown to also interact with other SOC candidates such as transient receptor potential channels (TRPCs) 1,

CD4+CD25+ regulatory T cells (T reg cells) play a key role in controlling autoimmunity and inflammation. Therefore, therapeutic agents that are capable of elevating numbers or increasing effector functions of this T cell subset are highly desirable. In a previous report we showed that a superagonistic monoclonal antibody specific for rat CD28 (JJ316) expands and activates T reg cells in vivo and upon short-term in vitro culture. Here we demonstrate that application of very low dosages of the CD28 superagonist into normal Lewis rats is sufficient to induce T reg cell expansion in vivo without the generalized lymphocytosis observed with high dosages of JJ316. Single i.v. administration of a low dose of the CD28 superagonist into Dark Agouti (DA) rats or Lewis rats that suffered from experimental autoimmune encephalomyelitis (EAE) proved to be highly and equally efficacious as high-dose treatment. Finally, we show that T reg cells that were isolated from CD28-treated animals displayed enhanced suppressive activity toward myelin basic protein–specific T cells in vitro, and, upon adoptive transfer, protected recipients from EAE. Our data indicate that this class of CD28-specific monoclonal antibodies targets CD4+CD25+ T reg cells and provides a novel means for the effective treatment of multiple sclerosis and other autoimmune diseases.

Store-operated Ca2؉ entry (SOCE) is believed to be of pivotal importance in T cell physiology. To test this hypothesis, we generated mice constitutively lacking the SOCE-regulating Ca 2؉ sensor stromal interaction molecule 1 (STIM1). In vitro analyses showed that SOCE and Ag receptor complex-triggered Ca 2؉ flux into STIM1-deficient T cells is virtually abolished. In vivo, STIM1-deficient mice developed a lymphoproliferative disease despite normal thymic T cell maturation and normal frequencies of CD4 ؉ Foxp3؉ regulatory T cells. Unexpectedly, STIM1-deficient bone marrow chimeric mice mounted humoral immune responses after vaccination and STIM1-deficient T cells were capable of inducing acute graft-versus-host disease following adoptive transfer into allogeneic hosts. These results demonstrate that STIM1-dependent SOCE is crucial for homeostatic T cell proliferation, but of much lesser importance for thymic T cell differentiation or T cell effector functions.

Background Intestinal microbiota and their metabolites (e.g. short-chain fatty acids (SCFAs)) may influence nonalcoholic fatty liver disease (NAFLD). Objective The objective of this article is to analyze gut bacterial diversity together with fecal SCFA concentrations and immunophenotyping of peripheral blood in histology-proven NAFLD patients. Methods Thirty-two NAFLD patients (14 nonalcoholic fatty liver (NAFL), 18 nonalcoholic steatohepatitis (NASH)) and 27 healthy controls (HCs)) were included in this study. Bacterial communities in feces were profiled by 16S ribosomal RNA gene sequencing of the V3–V4 region. Fecal SCFA levels were analyzed by high-performance liquid chromatography. Fluorescence-activated cell sorting analysis was performed of peripheral blood mononuclear cells. Results NASH patients were characterized by higher abundance of Fusobacteria and Fusobacteriaceae compared to NAFL and HCs. Conforming to our finding that NAFLD patients had higher fecal acetate and propionate levels, taxonomical differences of fecal bacteria were dominated by SCFA-producing bacteria. Higher fecal propionate and acetate levels were associated with lower resting regulatory T-cells (rTregs) (CD4+CD45RA+CD25++) as well as higher Th17/rTreg ratio in peripheral blood as immunological characteristics of NASH patients. Conclusions NASH patients are characterized by a different gut microbiome composition with higher fecal SCFA levels and higher abundance of SCFA-producing bacteria in NAFLD. These changes are associated with immunological features of disease progression. Our data suggest an important role of the intestinal microbiome and immunomodulatory bacterial metabolites in human NAFLD.

In recent years, the myocardium has been rediscovered under the lenses of immunology, and lymphocytes have been implicated in the pathogenesis of cardiomyopathies with different etiologies. Aging is an important risk factor for heart diseases, and it also has impact on the immune system. Thus, we sought to determine whether immunological activity would influence myocardial structure and function in elderly mice. Morphological, functional, and molecular analyses revealed that the age-related myocardial impairment occurs in parallel with shifts in the composition of tissueresident leukocytes and with an accumulation of activated CD4 + Foxp3 − (forkhead box P3) IFN-γ + T cells in the heart-draining lymph nodes. A comprehensive characterization of different aged immune-deficient mouse strains revealed that T cells significantly contribute to age-related myocardial inflammation and functional decline. Upon adoptive cell transfer, the T cells isolated from the mediastinal lymph node (med-LN) of aged animals exhibited increased cardiotropism, compared with cells purified from young donors or from other irrelevant sites. Nevertheless, these cells caused rather mild effects on cardiac functionality, indicating that myocardial aging might stem from a combination of intrinsic and extrinsic (immunological) factors. Taken together, the data herein presented indicate that heart-directed immune responses may spontaneously arise in the elderly, even in the absence of a clear tissue damage or concomitant infection. These observations might shed new light on the emerging role of T cells in myocardial diseases, which primarily affect the elderly population.T he myocardial cellular composition has been revisited in recent years, and leukocyte subsets residing in the healthy heart have been described (1-10). Cardiac-resident macrophages exhibiting an M2-like gene expression profile were found to be distributed in close association with the coronary vascular bed (3), and niches for dendritic cells (CD11c + MHC-II high CD80/86 low ) were found near the cardiac valves of the intact heart (1). It was also demonstrated that cardiac-resident MHCII + cells process and present myosin heavy chain-alpha-derived peptides under steady-state conditions (11, 12) and prime T cells ex vivo (1). However, whether lymphocytes can seed the intact myocardium and whether T-cell priming with myocardial antigens can occur in the absence of an infection or autoimmune myocarditis remain elusive.More recently, accumulating evidence indicated that noninfectious myocardial diseases are modulated by T cells. During the last couple of years, our group demonstrated that ischemic, sterile myocardial injuries can elicit lymphocyte activation directed against cardiac antigens (13-16). Our previous data, showing for the first time that CD4 + T cells reactive to cardiac components can foster the healing process that takes place after myocardial infarction, were corroborated by several other reports (13,15,(17)(18)(19)(20). However, these autoreactive T cells can also b...