CD4 ؉ CD25 ؉ regulatory T cells are essential in the protection from organ-specific autoimmune diseases. In the pancreas, they inhibit actions of autoreactive T cells and thereby prevent diabetes progression. The signals that control the generation, the maintenance, or the expansion of regulatory T cell pool in vivo remain poorly understood. Here we show that a transient pulse of transforming growth factor ␤ (TGF-␤) in the islets during the priming phase of diabetes is sufficient to inhibit disease onset by promoting the expansion of intraislet CD4 ؉ CD25 ؉ T cell pool. Approximately 40 -50% of intraislet CD4 ؉ T cells expressed the CD25 marker and exhibited characteristics of regulatory T cells including small size, high level of intracellular CTLA-4, expression of Foxp3, and transfer of protection against diabetes. Results from in vivo incorporation of BrdUrd revealed that the generation of a high frequency of regulatory T cells in the islets is due to in situ expansion upon TGF-␤ expression. Thus, these findings demonstrate a previously uncharacterized mechanism by which TGF-␤ inhibits autoimmune diseases via regulation of the size of the CD4 ؉ CD25 ؉ regulatory T cell pool in vivo.T ype I diabetes is an autoimmune disease that results from the failure of tolerance to beta-cell antigens (1). The mechanisms that have evolved to ensure discrimination between self and nonself are highly complex and not foolproof. Models of passive tolerance, such as thymic deletion of autoreactive T cells or nonreponsiveness in the periphery because of anergy or ignorance, cannot account for the presence of autoreactive T cells in healthy individuals despite the absence of the development of organ-specific autoimmune diseases. T cells endowed with suppressive function to control actions of autoreactive T cells were described decades ago and were thought originally to be a specialized T cell population the effect of which would be mediated by secreted antigen-specific factors (2). Nowadays, suppressor T cells (also referred to as regulatory T cells) are delineated into two cell subsets of natural regulatory (CD4 ϩ CD25 ϩ ) cells that emerge from the thymus (3, 4) and adaptive regulatory (CD4 ϩ CD25 Ϫ ) cells induced in the periphery to develop suppressive activity (5-7). However, this concept of dichotomous thymic CD25 ϩ versus adaptive CD25 Ϫ regulatory T cells has been challenged by several reports, supporting evidence for the peripheral generation of CD25 ϩ regulatory T cells in vivo and in vitro (8)(9)(10)(11)(12). The finding that suppressive functions are instructively programmed by the expression of Foxp3 finally provided the basis for integrating a unified model of regulatory T cell diversity (13-15). Forced expression of Foxp3 in CD4 ϩ CD25 Ϫ nonregulatory T cells, either by retroviral expression or in transgenic mice, showed acquisition of suppressive activity in vitro and inhibition of disease in vivo, inducing in a substantial proportion of Foxp3-bearing cells the expression of CD25 and GITR markers indicating that ex...

A variety of complement components have been detected on apoptotic cells and proposed to facilitate recognition and/or ingestion by phagocytes. The triggers for complement activation remain uncertain. To determine the role of IgM in classical pathway activation and clearance of apoptotic cells in vitro and in vivo, we quantified these parameters in mice deficient in serum IgM (sIgM). Phagocytosis by bone marrow-derived macrophages of apoptotic cells incubated with serum deficient in sIgM was markedly reduced, similar to apoptotic cells incubated with C1q deficient serum in vitro. Similarly, intraperitoneal clearance of apoptotic cells and cellular C3 deposition were significantly reduced in mice deficient in sIgM compared to wild-type mice. Clearance and C3 deposition were reconstituted by addback of IgM. In mice deficient in both sIgM and Clq, addback of both serum factors was required for restoration of clearance. These findings indicate that, on a quantitative basis, sIgM is a potent factor required for intraperitoneal phagocytosis of apoptotic cells, and further demonstrate that IgM and C1q work in concert to activate complement, resulting in C3 deposition on the apoptotic cell surface and ultimately, efficient clearance of the apoptotic cell by macrophages.

YS. p66Shc mediates high-glucose and angiotensin II-induced oxidative stress renal tubular injury via mitochondrial-dependent apoptotic pathway.

The immune system is constantly exposed to dying cells, most of which arise during central tolerance and from effete circulating immune cells. Under homeostatic conditions, phagocytes (predominantly macrophages and dendritic cells) belonging to the innate immune system, rapidly ingest cells and their debris. Apoptotic cell removal requires recognition of altered self on the apoptotic membrane, a process which is facilitated by natural antibodies and serum opsonins. Recognition, may be site and context specific. Uptake and ingestion of apoptotic cells promotes an immunosuppressive environment that avoids inflammatory responses to self-antigens. However, it does not preclude a T cell response and it is likely that constant exposure to self-antigen, particularly by immature dendritic cells, leads to T cell tolerance. Tolerance occurs by several different mechanisms including anergy and deletion (for CD8+T cells) and induction of T regulatory cells (for CD4+T cells). Failed apoptotic cell clearance promotes immune responses to self-antigens, especially when the cellular contents are leaked from the cell (necrosis). Inflammatory responses may be induced by nucleic acid stimulation of Toll like receptors and other immune sensors, specific intracellular proteins and non-protein (uric acid) stimulation of inflammasomes.

Monocytes differentiate into heterogeneous populations of tissue macrophages and dendritic cells (DCs) that regulate inflammation and immunity. Identifying specific populations of myeloid cells in vivo is problematic, however, because only a limited number of proteins have been used to assign cellular phenotype. Using mass spectrometry and bone marrow-derived cells, we provided a global view of the proteomes of M-CSF-derived macrophages, classically and alternatively activated macrophages, and GM-CSF-derived DCs. Remarkably, the expression levels of half the plasma membrane proteins differed significantly in the various populations of cells derived in vitro. Moreover, the membrane proteomes of macrophages and DCs were more distinct than those of classically and alternatively activated macrophages. Hierarchical cluster and dual statistical analyses demonstrated that each cell type exhibited a robust proteomic signature that was unique. To interrogate the phenotype of myeloid cells in vivo, we subjected elicited peritoneal macrophages harvested from wild-type and GM-CSF-deficient mice to mass spectrometric and functional analysis. Unexpectedly, we found that peritoneal macrophages exhibited many features of the DCs generated in vitro. These findings demonstrate that global analysis of the membrane proteome can help define immune cell phenotypes in vivo.

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Inflammatory bowel disease (IBD) is an intestinal immune-dysfunctional disease worldwide whose prevalence increasing in Asia including China. It is a chronic disease of the gastrointestinal tract with unknown cause. Exosomes are small vesicles in various body fluids. They have diameters of 40–120 nm, and one of their functions is long-distance transfer of various substances. In this study, we investigated the contents of salivary exosomes in patients with IBD and in healthy controls to explore a new biomarker in patients with IBD. In this study, whole saliva was obtained from patients with IBD (ulcerative colitis (UC), n = 37; Crohn’s disease (CD), n = 11) and apparently healthy individuals (HC, n = 10). Salivary exosomes were extracted from samples, and the proteins within the exosomes were identified by liquid chromatograph-mass spectrometer (LC-MS/MS). The results showed that more than 2000 proteins were detected in salivary exosomes from patients with IBD. Through gene ontology analysis, we found that proteasome subunit alpha type 7 (PSMA7) showed especially marked differences between patients with IBD and the healthy controls, in that its expression level was much higher in the CD and UC groups. This exosomal protein is related to proteasome activity and inflammatory responses. So we conclude that in this research, salivary exosomal PSMA7 was present at high levels in salivary exosomes from subjects with IBD. It can be a very promising biomarker to release the patients from the pain of colonoscopy.Electronic supplementary materialThe online version of this article (doi:10.1007/s13238-017-0413-7) contains supplementary material, which is available to authorized users.

Apoptotic cells must be rapidly cleared, as defects in this process can lead to autoimmunity. Milk fat globule EGF factor 8 (MFG-E8) binds to apoptotic cells and facilitates their removal through interaction with phagocytes. Mice deficient in MFG-E8 develop lupus-like autoimmunity associated with accumulation of apoptotic cells in vivo. Here, we have shown that MFG-E8 controls phagocytic ingestion of cell fragments as well as their intracellular processing into MHC-antigen complexes. Older Mfge8 -/-mice spontaneously developed dermatitis associated with CD8 + T cell infiltration and striking activation of effector memory CD8 + T cells. CD8 + T cell responses to both exogenous and endogenous apoptotic cell-associated antigens were enhanced in Mfge8 -/-mice. MFG-E8 deficiency accelerated the onset of disease in a mouse model of autoimmune diabetes. Enhanced CD8 + T cell responses were attributed to increased cross-presentation by DCs along with increased detection of antigen-MHCI complexes. Intracellular trafficking analysis revealed that intact apoptotic cells ingested by wild-type DCs rapidly fused with lysosomes, whereas smaller fragments persisted in Mfge8 -/-DC endosomal compartments for 24 hours. These observations suggest that MFG-E8 deficiency promotes immune responses to self antigens not only by delaying the clearance of dying cells but also by altering intracellular processing, leading to enhanced self-antigen presentation.