Autoimmune CD4+ T cells fine-tune TCF1 expression to maintain function and survive persistent antigen exposure during diabetes.

Self-reactive T cells experience chronic antigen exposure but do not exhibit signs of exhaustion. Here, we investigated the mechanisms for sustained, functioning autoimmune CD4+ T cells despite chronic stimulation. Examination of T cell priming showed that CD4+ T cells activated in the absence of infectious signals retained TCF1 expression. At later time points and during blockade of new T cell recruitment, most islet-infiltrating autoimmune CD4+ T cells were TCF1+, although expression was reduced on a per T cell basis. The Tcf7 locus was epigenetically modified in circulating autoimmune CD4+ T cells, suggesting a pre-programmed de novo methylation of the locus in early stages of autoimmune CD4+ T cell differentiation. This mirrored the epigenetic profile of recently recruited CD4+CD62L+ T cells in the pancreas. Collectively, these data reveal a unique environment during autoimmune CD4+ T cell priming that allows T cells to fine-tune TCF1 expression and maintain long-term survival and function.

OCA-B/Pou2af1 is sufficient to promote CD4+ T cell memory and prospectively identifies memory precursors.

The molecular mechanisms leading to the establishment of immunological memory are inadequately understood, limiting the development of effective vaccines and durable antitumor immune therapies. Here, we show that ectopic OCA-B expression is sufficient to improve antiviral memory recall responses, while having minimal effects on primary effector responses. At peak viral response, short-lived effector T cell populations are expanded but show increased Gadd45b and Socs2 expression, while memory precursor effector cells show increased expression of Bcl2, Il7r, and Tcf7 on a per-cell basis. Using an OCA-B mCherry reporter mouse line, we observe high OCA-B expression in CD4+ central memory T cells. We show that early in viral infection, endogenously elevated OCA-B expression prospectively identifies memory precursor cells with increased survival capability and memory recall potential. Cumulatively, the results demonstrate that OCA-B is both necessary and sufficient to promote CD4 T cell memory in vivo and can be used to prospectively identify memory precursor cells.

Tet2 deletion in CD4+ T cells disrupts Th1 lineage commitment in memory cells and enhances T follicular helper cell recall responses to viral rechallenge.

Following viral clearance, antigen-specific CD4+ T cells contract and form a pool of distinct Th1 and Tfh memory cells that possess unique epigenetic programs, allowing them to rapidly recall their specific effector functions upon rechallenge. DNA methylation programing mediated by the methylcytosine dioxygenase Tet2 contributes to balancing Th1 and Tfh cell differentiation during acute viral infection; however, the role of Tet2 in CD4+ T cell memory formation and recall is unclear. Using adoptive transfer models of antigen-specific wild type and Tet2 knockout CD4+ T cells, we find that Tet2 is required for full commitment of CD4+ T cells to the Th1 lineage and that in the absence of Tet2, memory cells preferentially recall a Tfh like phenotype with enhanced expansion upon secondary challenge. These findings demonstrate an important role for Tet2 in enforcing lineage commitment and programing proliferation potential, and highlight the potential of targeting epigenetic programing to enhance adaptive immune responses.

Cross-Priming Dendritic Cells Exacerbate Immunopathology After Ischemic Tissue Damage in the Heart.

BACKGROUND: Ischemic heart disease is a leading cause of heart failure and despite advanced therapeutic options, morbidity and mortality rates remain high. Although acute inflammation in response to myocardial cell death has been extensively studied, subsequent adaptive immune activity and anti-heart autoimmunity may also contribute to the development of heart failure. After ischemic injury to the myocardium, dendritic cells (DC) respond to cardiomyocyte necrosis, present cardiac antigen to T cells, and potentially initiate a persistent autoimmune response against the heart. Cross-priming DC have the ability to activate both CD4+ helper and CD8+ cytotoxic T cells in response to necrotic cells and may thus be crucial players in exacerbating autoimmunity targeting the heart. This study investigates a role for cross-priming DC in post-myocardial infarction immunopathology through presentation of self-antigen from necrotic cardiac cells to cytotoxic CD8+ T cells. METHODS: We induced type 2 myocardial infarction-like ischemic injury in the heart by treatment with a single high dose of the ß-adrenergic agonist isoproterenol. We characterized the DC population in the heart and mediastinal lymph nodes and analyzed long-term cardiac immunopathology and functional decline in wild type and Clec9a-depleted mice lacking DC cross-priming function. RESULTS: A diverse DC population, including cross-priming DC, is present in the heart and activated after ischemic injury. Clec9a-/- mice deficient in DC cross-priming are protected from persistent immune-mediated myocardial damage and decline of cardiac function, likely because of dampened activation of cytotoxic CD8+ T cells. CONCLUSION: Activation of cytotoxic CD8+ T cells by cross-priming DC contributes to exacerbation of postischemic inflammatory damage of the myocardium and corresponding decline in cardiac function. Importantly, this provides novel therapeutic targets to prevent postischemic immunopathology and heart failure.

Enhancing the efficacy of glycolytic blockade in cancer cells via RAD51 inhibition.

Targeting the early steps of the glycolysis pathway in cancers is a well-established therapeutic strategy; however, the doses required to elicit a therapeutic effect on the cancer can be toxic to the patient. Consequently, numerous preclinical and clinical studies have combined glycolytic blockade with other therapies. However, most of these other therapies do not specifically target cancer cells, and thus adversely affect normal tissue. Here we first show that a diverse number of cancer models - spontaneous, patient-derived xenografted tumor samples, and xenografted human cancer cells - can be efficiently targeted by 2-deoxy-D-Glucose (2DG), a well-known glycolytic inhibitor. Next, we tested the cancer-cell specificity of a therapeutic compound using the MEC1 cell line, a chronic lymphocytic leukemia (CLL) cell line that expresses activation induced cytidine deaminase (AID). We show that MEC1 cells, are susceptible to 4,4'-Diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS), a specific RAD51 inhibitor. We then combine 2DG and DIDS, each at a lower dose and demonstrate that this combination is more efficacious than fludarabine, the current standard- of- care treatment for CLL. This suggests that the therapeutic blockade of glycolysis together with the therapeutic inhibition of RAD51-dependent homologous recombination can be a potentially beneficial combination for targeting AID positive cancer cells with minimal adverse effects on normal tissue. Implications: Combination therapy targeting glycolysis and specific RAD51 function shows increased efficacy as compared to standard of care treatments in leukemias.

Systemic autoimmunity induced by the TLR7/8 agonist Resiquimod causes myocarditis and dilated cardiomyopathy in a new mouse model of autoimmune heart disease.

Systemic autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) show significant heart involvement and cardiovascular morbidity, which can be due to systemically increased levels of inflammation or direct autoreactivity targeting cardiac tissue. Despite high clinical relevance, cardiac damage secondary to systemic autoimmunity lacks inducible rodent models. Here, we characterise immune-mediated cardiac tissue damage in a new model of SLE induced by topical application of the Toll-like receptor 7/8 (TLR7/8) agonist Resiquimod. We observe a cardiac phenotype reminiscent of autoimmune-mediated dilated cardiomyopathy, and identify auto-antibodies as major contributors to cardiac tissue damage. Resiquimod-induced heart disease is a highly relevant mouse model for mechanistic and therapeutic studies aiming to protect the heart during autoimmunity.