A THEMIS:SHP1 complex promotes T‐cell survival

THEMIS is critical for conventional T‐cell development, but its precise molecular function remains elusive. Here, we show that THEMIS constitutively associates with the phosphatases SHP1 and SHP2. This complex requires the adapter GRB2, which bridges SHP to THEMIS in a Tyr‐phosphorylation‐independent fashion. Rather, SHP1 and THEMIS engage with the N‐SH3 and C‐SH3 domains of GRB2, respectively, a configuration that allows GRB2‐SH2 to recruit the complex onto LAT. Consistent with THEMIS‐mediated recruitment of SHP to the TCR signalosome, THEMIS knock‐down increased TCR‐induced CD3‐ζ phosphorylation, Erk activation and CD69 expression, but not LCK phosphorylation. This generalized TCR signalling increase led to augmented apoptosis, a phenotype mirrored by SHP1 knock‐down. Remarkably, a KI mutation of LCK Ser59, previously suggested to be key in ERK‐mediated resistance towards SHP1 negative feedback, did not affect TCR signalling nor ligand discrimination in vivo. Thus, the THEMIS:SHP complex dampens early TCR signalling by a previously unknown molecular mechanism that favours T‐cell survival. We discuss possible implications of this mechanism in modulating TCR output signals towards conventional T‐cell development and differentiation.     

Large‐scale proteomic analysis of tyrosine‐phosphorylation induced by T‐cell receptor or B‐cell receptor activation reveals new signaling pathways

Activation of the T‐cell receptor (TCR) and that of the B‐cell receptor (BCR) elicits tyrosine‐phosphorylation of proteins that belongs to similar functional categories, but result in distinct cellular responses. Large‐scale analyses providing an overview of the signaling pathways downstream of TCR or BCR have not been described, so it has been unclear what components of these pathways are shared and which are specific. We have now performed a systematic analysis and provide a comprehensive list of tyrosine‐phosphorylated proteins (PY proteome) with quantitative data on their abundance in T cell, B cell, and nonlymphoid cell lines. Our results led to the identification of novel tyrosine‐phosphorylated proteins and signaling pathways not previously implicated in immunoreceptor signal transduction, such as clathrin, zonula occludens 2, eukaryotic translation initiation factor 3, and RhoH, suggesting that TCR or BCR signaling may be linked to downstream processes such as endocytosis, cell adhesion, and translation. Thus comparative and quantitative studies of tyrosine‐phosphorylation have the potential to expand knowledge of signaling networks and to promote understanding of signal transduction at the system level.     

Proteomics and Network Analyses Reveal Inhibition of Akt‐mTOR Signaling in CD4+ T Cells by Mycobacterium tuberculosis Mannose‐Capped Lipoarabinomannan

Mycobacterium tuberculosis (Mtb) cell wall glycolipid mannose‐capped lipoarabinomannan (ManLAM) inhibits CD4⁺ T‐cell activation by inhibiting proximal T‐cell receptor (TCR) signaling when activated by anti‐CD3. To understand the impact of ManLAM on CD4⁺ T‐cell function when both the TCR–CD3 complex and major costimulator CD28 are engaged, we performed label‐free quantitative MS and network analysis. Mixed‐effect model analysis of peptide intensity identified 149 unique peptides representing 131 proteins that were differentially regulated by ManLAM in anti‐CD3‐ and anti‐CD28‐activated CD4⁺ T cells. Crosstalker, a novel network analysis tool identified dysregulated translation, TCA cycle, and RNA metabolism network modules. PCNA, Akt, mTOR, and UBC were found to be bridge node proteins connecting these modules of dysregulated proteins. Altered PCNA expression and cell cycle analysis showed arrest at the G2M phase. Western blot confirmed that ManLAM inhibited Akt and mTOR phosphorylation, and decreased expression of deubiquitinating enzymes Usp9x and Otub1. Decreased NF‐κB phosphorylation suggested interference with CD28 signaling through inhibition of the Usp9x‐Akt‐mTOR pathway. Thus, ManLAM induced global changes in the CD4⁺ T‐cell proteome by affecting Akt‐mTOR signaling, resulting in broad functional impairment of CD4⁺ T‐cell activation beyond inhibition of proximal TCR–CD3 signaling.     

Tonic ubiquitylation controls T‐cell receptor:CD3 complex expression during T‐cell development

Expression of the T‐cell receptor (TCR):CD3 complex is tightly regulated during T‐cell development. The mechanism and physiological role of this regulation are unclear. Here, we show that the TCR:CD3 complex is constitutively ubiquitylated in immature double positive (DP) thymocytes, but not mature single positive (SP) thymocytes or splenic T cells. This steady state, tonic CD3 monoubiquitylation is mediated by the CD3ε proline‐rich sequence, Lck, c‐Cbl, and SLAP, which collectively trigger the dynamin‐dependent downmodulation, lysosomal sequestration and degradation of surface TCR:CD3 complexes. Blocking this tonic ubiquitylation by mutating all the lysines in the CD3 cytoplasmic tails significantly upregulates TCR levels on DP thymocytes. Mimicking monoubiquitylation by expression of a CD3ζ‐monoubiquitin (monoUb) fusion molecule significantly reduces TCR levels on immature thymocytes. Moreover, modulating CD3 ubiquitylation alters immunological synapse (IS) formation and Erk phosphorylation, thereby shifting the signalling threshold for positive and negative selection, and regulatory T‐cell development. Thus, tonic TCR:CD3 ubiquitylation results in precise regulation of TCR expression on immature T cells, which is required to maintain the fidelity of T‐cell development.     

Increased T‐cell stimulating activity by mutated SEC2 correlates with its improved antitumour potency

Aims: To investigate the improved antitumour activity of SAM‐3 compared with recombinant staphylococcal enterotoxins C2 (rSEC2). Methods and Results: Methylthiazol tetrazolium and flow cytometry assays showed that the antitumour activity of SAM‐3 in vivo was improved because of enhanced T‐cell stimulating potency, resulting in massive activation of T cells, particularly CD4 ⁺ and CD8 ⁺ T cells, and subsequent cytokine release. Quantitative real‐time PCR assay showed that despite similar Vβ specificities induced by rSEC2 and SAM‐3, the quantities of activated T cells bearing specific Vβin vitro were different. Conclusions: The results strongly suggested that the increased SAM‐3–T‐cell receptor (TCR) binding affinity contributed to massive T‐cell activation and cytokine release, substantially amplifying antitumour immune response in vivo. Significance and Impact of the Study: This study provided evidence for the mechanism of SAM‐3 antitumour activity improvement compared with rSEC2. Results indicated that SAM‐3 could be used as a potent powerful candidate agent for tumour treatment in clinics.     

The versatility of the αβ T‐cell antigen receptor

The T‐cell antigen receptor is a heterodimeric αβ protein (TCR) expressed on the surface of T‐lymphocytes, with each chain of the TCR comprising three complementarity‐determining regions (CDRs) that collectively form the antigen‐binding site. Unlike antibodies, which are closely related proteins that recognize intact protein antigens, TCRs classically bind, via their CDR loops, to peptides (p) that are presented by molecules of the major histocompatibility complex (MHC). This TCR‐pMHC interaction is crucially important in cell‐mediated immunity, with the specificity in the cellular immune response being attributable to MHC polymorphism, an extensive TCR repertoire and a variable peptide cargo. The ensuing structural and biophysical studies within the TCR‐pMHC axis have been highly informative in understanding the fundamental events that underpin protective immunity and dysfunctional T‐cell responses that occur during autoimmunity. In addition, TCRs can recognize the CD1 family, a family of MHC‐related molecules that instead of presenting peptides are ideally suited to bind lipid‐based antigens. Structural studies within the CD1‐lipid antigen system are beginning to inform us how lipid antigens are specifically presented by CD1, and how such CD1‐lipid antigen complexes are recognized by the TCR. Moreover, it has recently been shown that certain TCRs can bind to vitamin B based metabolites that are bound to an MHC‐like molecule termed MR1. Thus, TCRs can recognize peptides, lipids, and small molecule metabolites, and here we review the basic principles underpinning this versatile and fascinating receptor recognition system that is vital to a host's survival.     

Co‐recruitment analysis of the CBL and CBLB signalosomes in primary T cells identifies CD5 as a key regulator of TCR‐induced ubiquitylation

T‐cell receptor (TCR) signaling is essential for the function of T cells and negatively regulated by the E3 ubiquitin–protein ligases CBL and CBLB. Here, we combined mouse genetics and affinity purification coupled to quantitative mass spectrometry to monitor the dynamics of the CBL and CBLB signaling complexes that assemble in normal T cells over 600 seconds of TCR stimulation. We identify most previously known CBL and CBLB interacting partners, as well as a majority of proteins that have not yet been implicated in those signaling complexes. We exploit correlations in protein association with CBL and CBLB as a function of time of TCR stimulation for predicting the occurrence of direct physical association between them. By combining co‐recruitment analysis with biochemical analysis, we demonstrated that the CD5 transmembrane receptor constitutes a key scaffold for CBL‐ and CBLB‐mediated ubiquitylation following TCR engagement. Our results offer an integrated view of the CBL and CBLB signaling complexes induced by TCR stimulation and provide a molecular basis for their negative regulatory function in normal T cells.     

Generation of CD4CreERT2 transgenic mice to study development of peripheral CD4‐T‐cells

After thymic emigration CD4‐T‐cells continue to differentiate into multiple effector and suppressor sublineages in peripheral lymphoid organs. In vivo analysis of peripheral CD4‐T‐cell differentiation has relied on animal models with targeted gene mutations. These are expressed either constitutively or conditionally after Cre mediated recombination. Available Cre transgenic strains to specifically target T‐cells act at stages of thymocyte development that precede thymic selection. Tracing gene functions in CD4‐T‐cell development after thymic exit becomes complicated when the targeted gene is essential during thymic development. Other approaches to conditionally modify gene functions in peripheral T‐cells involve infection of in vitro activated cells with Cre expressing lenti‐, retro‐, or adenoviruses, which precludes in vivo analyses. To study molecular mechanisms of peripheral CD4‐T‐cell differentiation in vivo and in vitro we generated transgenic mice expressing a tamoxifen inducible Cre recombinase (CreER^T2) under the control of the CD4 gene promoter. We show here that in CD4CreER^T2 mice Cre is inducibly and selectively activated in CD4‐T‐cells. Tamoxifen treatment both in vivo and in vitro results in efficient recombination of loci marked by LoxP sites. Moreover, this strain shows no abnormalities related to transgene insertion. Therefore it provides a valuable tool for studying gene function during differentiation of naïve peripheral CD4‐T‐cells into effector or suppressor sub‐lineages. genesis 50:908–913, 2012. © 2012 Wiley Periodicals, Inc.     

Hyper‐reactive cloned mice generated by direct nuclear transfer of antigen‐specific CD4+ T cells

T‐cell receptor (TCR)‐transgenic mice have been employed for evaluating antigen‐response mechanisms, but their non‐endogenous TCR might induce immune response differently than the physiologically expressed TCR. Nuclear transfer cloning produces animals that retain the donor genotype in all tissues including germline and immune systems. Taking advantage of this feature, we generated cloned mice that carry endogenously rearranged TCR genes from antigen‐specific CD4⁺ T cells. We show that T cells of the cloned mice display distinct developmental pattern and antigen reactivity because of their endogenously pre‐rearranged TCRα (rTα) and TCRβ (rTβ) alleles. These alleles were transmitted to the offspring, allowing us to establish a set of mouse lines that show chronic‐type allergic phenotypes, that is, bronchial and nasal inflammation, upon local administrations of the corresponding antigens. Intriguingly, the existence of either rTα or rTβ is sufficient to induce in vivo hypersensitivity. These cloned mice expressing intrinsic promoter‐regulated antigen‐specific TCR are a unique animal model with allergic predisposition for investigating CD4⁺ T‐cell‐mediated pathogenesis and cellular commitment in immune diseases.     

Development of CD8+ T cells expressing two distinct receptors specific for MTB and HIV‐1 peptides

The immune response in individuals co‐infected with Mycobacterium tuberculosis (MTB) and the human immunodeficiency virus (MTB/HIV) gradually deteriorates, particularly in the cellular compartment. Adoptive transfer of functional effector T cells can confer protective immunity to immunodeficient MTB/HIV co‐infected recipients. However, few such effector T cells exist in vivo, and their isolation and amplification to sufficient numbers is difficult. Therefore, enhancing immune responses against both pathogens is critical for treating MTB/HIV co‐infected patients. One approach is adoptive transfer of T cell receptor (TCR) gene‐modified T cells for the treatment of MTB/HIV co‐infections because lymphocyte numbers and their functional avidity is significantly increased by TCR gene transfer. To generate bispecific CD8⁺ T cells, MTB Ag85B_199–207 peptide‐specific TCRs (MTB/TCR) and HIV‐1 Env_120–128 peptide‐specific TCRs (HIV/TCR) were isolated and introduced into CD8⁺ T cells simultaneously using a retroviral vector. To avoid mispairing among exogenous and endogenous TCRs, and to improve the function and stability of the introduced TCRs, several strategies were employed, including introducing mutations in the MTB/TCR constant (C) regions, substituting part of the HIV/TCR C regions with CD3ζ, and linking gene segments with three different 2A peptides. Results presented in this report suggest that the engineered T cells possessed peptide‐specific specificity resulting in cytokine production and cytotoxic activity. This is the first report describing the generation of engineered T cells specific for two different pathogens and provides new insights into TCR gene therapy for the treatment of immunocompromised MTB/HIV co‐infected patients.     

Relative roles of T‐cell receptor ligands and interleukin‐2 in driving T‐cell proliferation

Stimulation of T cells by the T‐cell receptor (TCR)/CD3 complex results in interleukin‐2 (IL‐2) synthesis and surface expression of the IL‐2 receptor (IL‐2R), which in turn drive T‐cell proliferation. However, the significance of the requirement of IL‐2 in driving T‐cell proliferation, when TCR stimulation itself delivers potential mitogenic signals, is unclear. We show that blocking of IL‐2 synthesis by Cyclosporin A (CsA) suppressed both the Concanavalin A (Con A)‐ and phorbol myristate acetate (PMA)/ionomycin‐induced proliferation of T cells. The latter is also inhibited by anti‐IL‐2R. Kinetic studies showed that T‐cell proliferation begins to become resistant to CsA inhibition by about 12 h and became largely resistant by 18 h of stimulation. PMA, the protein kinase C activator, enhanced Con A‐induced T‐cell proliferation if added only within first 12 h of stimulation, and not after that. Given the fact that, in the present study, TCR is downregulated within 2 h of Con A stimulation and T cells entered the S phase of cell cycle by about 18 h of stimulation, the above results suggest that TCR stimulation provides the initial trigger to the resting T cells, which allows the cells to traverse the first two third portions of G1 phase of cell cycle and become proliferation competent. IL‐2 action begins afterward, delivering the actual proliferation signal(s), allowing the cells to traverse the rest of G1 phase and enter the S phase of the cell cycle. J. Cell. Biochem. 76:37–43, 1999. © 1999 Wiley‐Liss, Inc.     

AKT isoforms modulate Th1‐like Treg generation and function in human autoimmune disease

Foxp3⁺ regulatory T cells (Tregs) exhibit plasticity, which dictates their function. Secretion of the inflammatory cytokine IFNγ, together with the acquisition of a T helper 1 (Th1)‐like effector phenotype as observed in cancer, infection, and autoimmune diseases, is associated with loss of Treg suppressor function through an unknown mechanism. Here, we describe the signaling events driving the generation of human Th1‐Tregs. Using a genome‐wide gene expression approach and pathway analysis, we identify the PI3K/AKT/Foxo1/3 signaling cascade as the major pathway involved in IFNγ secretion by human Tregs. Furthermore, we describe the opposing roles of AKT isoforms in Th1‐Treg generation ex vivo. Finally, we employ multiple sclerosis as an in vivo model with increased but functionally defective Th1‐Tregs. We show that the PI3K/AKT/Foxo1/3 pathway is activated in ex vivo‐isolated Tregs from untreated relapsing–remitting MS patients and that blockade of the pathway inhibits IFNγ secretion and restores the immune suppressive function of Tregs. These data define a fundamental pathway regulating the function of human Tregs and suggest a novel treatment paradigm for autoimmune diseases.     

Integration of conventional quantitative and phospho‐proteomics reveals new elements in activated Jurkat T‐cell receptor pathway maintenance

Recent years have seen a constant development of tools for the global assessment of phosphoproteins. Here, we outline a concept for integrating approaches for quantitative proteomics and phosphoproteomics. The strategy was applied to the analysis of changes in signalling and protein synthesis occurring after activation of the T‐cell receptor (TCR) pathway in a T‐cell line (Jurkat cells). For this purpose, peptides were obtained from four biological replicates of activated and control Jurkat T‐cells and phosphopeptides enriched via a TiO₂‐based chromatographic step. Both phosphopeptide‐enriched and flow‐through fractions were analyzed by LC–MS. We observed 1314 phosphopeptides in the enriched fraction whereas 19 were detected in the flow‐through, enabling the quantification of 414 and eight phosphoproteins in the respective fractions. Pathway analysis revealed the differential regulation of many metabolic pathways. Among the quantified proteins, 11 kinases with known TCR‐related function were detected. A kinase‐substrate database search for the phosphosites identified also confirmed the activity of a further ten kinases. In total, these two approaches provided evidence of 19 unique TCR‐related kinases. The combination of phosphoproteomics and conventional quantitative shotgun analysis leads to a more comprehensive assessment of the signalling networks needed for the maintenance of the activated status of Jurkat T‐cells.     

Molecular properties of gp100‐reactive T‐cell receptors drive the cytokine profile and antitumor efficacy of transgenic host T cells

To study the contribution of T‐cell receptors (TCR) to resulting T‐cell responses, we studied three different human αβ TCRs, reactive to the same gp100‐derived peptide presented in the context of HLA‐A*0201. When expressed in primary CD8 T cells, all receptors elicited classic antigen‐induced IFN‐γ responses, which correlated with TCR affinity for peptide–MHC in the order T4H2 > R6C12 > SILv44. However, SILv44 elicited superior IL‐17A release. Importantly, in vivo, SILv44‐transgenic T cells mediated superior antitumor responses to 888‐A2 + human melanoma tumor cells upon adoptive transfer into tumor‐challenged mice while maintaining IL‐17 expression. Modeling of the TCR ternary complexes suggested architectural differences between SILv44 and the other complexes, providing a potential structural basis for the observed differences. Overall, the data reveal a more prominent role for the T‐cell receptor in defining host T‐cell physiology than traditionally assumed, while parameters beyond IFN‐γ secretion and TCR affinity ultimately determine the reactivity of tumor‐reactive T cells.     

Autoreactive T‐cell receptor (Vβ/D/Jβ) sequences in diabetes are homologous to insulin,glucagon, the insulin receptor,and the glucagon receptor

The hypervariable (Vβ/D/Jβ) regions of T‐cell receptors (TCR) have been sequenced in a variety of autoimmune diseases by various investigators. An analysis of some of these sequences shows that TCR from both human diabetics and NOD mice mimic insulin, glucagon, the insulin receptor, and the glucagon receptor. Such similarities are not found in the TCR produced in other human autoimmune diseases. These data may explain how insulin, glucagon, and their receptors are targets of autoimmunity in diabetes and also suggest that TCR mimicking insulin and its receptor may be targets of anti‐insulin autoantibodies. Such intra‐systemic mimicry of self‐proteins also raises complex questions about how “self” and “nonself” are regulated during TCR production, especially in light of the complementarity of insulin for its receptor and glucagon for its receptor. The data presented here suggest that some TCR may be complementary to other TCR in autoimmune diseases, a possibility that is experimentally testable. Such complementarity, if it exists, could either serve to down‐regulate the clones bearing such TCR or, alternatively, trigger an intra‐immune system civil war between them. Copyright © 2008 John Wiley & Sons, Ltd.     

Eupatilin inhibits T‐cell activation by modulation of intracellular calcium flux and NF‐κB and NF‐AT activity

Eupatilin, one of the pharmacologically active ingredients of Artemisia princeps, exhibits a potent anti‐ulcer activity, but its effects on T‐cell immunity have not been investigated. Here, we show that eupatilin has a profound inhibitory effect on IL‐2 production in Jurkat T cells as well as in human peripheral blood leukocytes. Eupatilin neither influenced clustering of CD3 and LFA‐1 to the immunological synapse nor inhibited conjugate formation between T cells and B cells in the presence or absence of superantigen (SEE). Eupatilin also failed to inhibit T‐cell receptor (TCR) internalization, thereby, suggesting that eupatilin does not interfere with TCR‐mediated signals on the membrane proximal region. In unstimulated T cells, eupatilin significantly induced apoptotic cell death, as evidenced by an increased population of annexin V⁺/PI⁺ cells and cleavage of caspase‐3 and PARP. To our surprise, however, once cells were activated, eupatilin had little effect on apoptosis, and instead slightly protected cells from activation‐induced cell death, suggesting that apoptosis also is not a mechanism for eupatilin‐induced T‐cell suppression. On the contrary, eupatilin dramatically inhibited I‐κBα degradation and NF‐AT dephosphorylation and, consequently, inhibited NF‐κB and NF‐AT promoter activities in PMA/A23187‐stimulated T cells. Interestingly, intracellular calcium flux was significantly perturbed in cells pre‐treated with eupatilin, suggesting that calcium‐dependent cascades might be targets for eupatilin action. Collectively, our results provide evidence for dual regulatory functions of eupatilin: (1) a pro‐apoptotic effect on resting T cells and (2) an immunosuppressive effect on activated T cells, presumably through modulation of Ca²⁺ flux. J. Cell. Biochem. 108: 225–236, 2009. © 2009 Wiley‐Liss, Inc.     

Interleukin‐21 administration to aged mice rejuvenates their peripheral T‐cell pool by triggering de novo thymopoiesis

The vaccination efficacy in the elderly is significantly reduced compared to younger populations due to thymic involution and age‐related intrinsic changes affecting their naïve T‐cell compartment. Interleukin (IL)‐21 was recently shown to display thymostimulatory properties. Therefore, we hypothesized that its administration to ageing hosts may improve T‐cell output and thus restore a competent peripheral T‐cell compartment. Indeed, an increase in the production of recent thymic emigrants (RTEs) attributable to intrathymic expansion of early thymic progenitors (ETPs), double‐negative (DN), and double‐positive (DP) thymocytes as well as thymic epithelial cell (TEC) was observed in recombinant (r)IL‐21‐treated aged mice. In sharp contrast, no alterations in the frequency of bone marrow (BM)‐derived progenitors were detected following rIL‐21 administration. Enhanced production of naïve T cells improved the T‐cell receptor (TCR) repertoire diversity and re‐established a pool of T cells exhibiting higher levels of miR‐181a and diminished amounts of the TCR‐inhibiting phosphatases SHP‐2 and DUSP5/6. As a result, stimulation of T cells derived from rIL‐21‐treated aged mice displayed enhanced activation of Lck, ZAP‐70, and ERK, which ultimately boosted their IL‐2 production, CD25 expression, and proliferation capabilities in comparison with T cells derived from control aged mice. Consequently, aged rIL‐21‐treated mice vaccinated using a tyrosinase‐related protein 2 (Trp2)‐derived peptide exhibited a substantial delay in B16 tumor growth and improved survival. The results of this study highlight the immunorestorative function of rIL‐21 paving its use as a strategy for the re‐establishment of effective immunity in the elderly.     

n‐3 Fatty Acids Modulate T‐Cell Calcium Signaling in Obese Macrosomic Rats

Objective: We investigated the effects of a diet containing EPAX‐7010, rich in PUFAs such as eicosapentaenoic acid [20:5(n‐3)] and docosahexaenoic acid [22:6(n‐3)], i.e., a PUFA/EPAX regimen, on T‐cell activation in diabetic pregnant rats and their obese pups. Research Methods and Procedures: Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on Day 5 of gestation. T‐cell blastogenesis was assayed by using ³H‐thymidine, whereas intracellular free calcium concentrations ([Ca²⁺]i) were measured by using Fura‐2 in diabetic pregnant rats and their obese offspring. Results: Concavalin‐A‐stimulated T‐cell proliferation was decreased in both pregnant diabetic rats and their obese pups as compared with control animals. Feeding the PUFA/EPAX diet restored T‐cell proliferation in both groups of animals. We also employed ionomycin, which at 50 nM opens calcium channels, and thapsigargin (TG), which recruits [Ca²⁺]i from endoplasmic reticulum pool. We observed that ionomycin‐induced increases in [Ca²⁺]i in T‐cells of diabetic mothers and obese offspring were greater than in those of control rats. Furthermore, feeding PUFA/EPAX diet diminished significantly the ionomycin‐evoked rise in [Ca²⁺]i in diabetic and obese animals. TG‐induced increases in [Ca²⁺]i in T‐cells of diabetic pregnant rats and their obese offspring were greater than in those of control rats. The feeding of the experimental diet significantly curtailed the TG‐evoked increases in [Ca²⁺]i in both diabetic and obese rats. Discussion: Together, these observations provide evidence that T‐cell activation and T‐cell calcium signaling are altered during gestational diabetes and macrosomia. Hence, dietary fish oils, particularly eicosapentaenoic acid and docosahexaenoic acid, may restore these T‐cell abnormalities.     

Special AT‐rich sequence binding protein 1 is required for maintenance of T cell receptor responsiveness and development of experimental autoimmune encephalomyelitis

The genome organizer special AT‐rich sequence binding protein 1 (SATB1) regulates specific functions through chromatin remodeling in T helper cells. It was recently reported by our team that T cells from SATB1 conditional knockout (SATB1cKO) mice, in which the Satb1 gene is deleted from hematopoietic cells, impair phosphorylation of signaling molecules in response to T cell receptor (TCR) crosslinking. However, in vivo T cell responses upon antigen presentation in the absence of SATB1 remain unclear. In the current study, it was shown that SATB1 modulates T cell antigen responses during the induction and effector phases. Expression of SATB1 was upregulated in response to TCR stimulation, suggesting that SATB1 is important for this antigen response. The role of SATB1 in TCR responses and induced experimental autoimmune encephalomyelitis (EAE) was therefore examined using the myelin oligodendrocyte glycoprotein peptide 35‐55 (MOG35‐55) and pertussis toxin. SATB1cKO mice were found to be resistant to EAE and had defects in IL‐17‐ and IFN‐γ‐producing pathogenic T cells. Thus, SATB1 expression appears necessary for T cell function in the induction phase. To examine SATB1 function during the effector phase, a tamoxifen‐inducible SATB1 deletion system, SATB1cKO‐ER‐Cre mice, was used. Encephalitogenic T cells from MOG35‐55‐immunized SATB1cKO‐ER‐Cre mice were transferred into healthy mice. Mice that received tamoxifen before the onset of paralysis were resistant to EAE. Furthermore, no disease progression occurred in recipient mice treated with tamoxifen after the onset of EAE. Thus, SATB1 is essential for maintaining TCR responsiveness during the induction and effector phases and may provide a novel therapeutic target for T cell‐mediated autoimmune diseases.