Initiation of Autoimmune Diabetes by Developmentally Regulated Presentation of Islet Cell Antigens in the Pancreatic Lymph Nodes

Little is known about the events triggering lymphocyte invasion of the pancreatic islets in prelude to autoimmune diabetes. For example, where islet-reactive T cells first encounter antigen has not been identified. We addressed this issue using BDC2.5 T cell receptor transgenic mice, which express a receptor recognizing a natural islet beta cell antigen. In BDC2.5 animals, activated T cells were found only in the islets and the lymph nodes draining them, and there was a close temporal correlation between lymph node T cell activation and islet infiltration. When naive BDC2.5 T cells were transferred into nontransgenic recipients, proliferating cells were observed only in pancreatic lymph nodes, and this occurred significantly before insulitis was detectable. Surprisingly, proliferation was not seen in 10-day-old recipients. This age-dependent dichotomy was reproduced in a second transfer system based on an unrelated antigen artificially expressed on beta cells. We conclude that beta cell antigens are transported specifically to pancreatic lymph nodes, where they trigger reactive T cells to invade the islets. Systemic or extrapancreatic T cell priming, indicative of activation via molecular mimicry or superantigens, was not seen. Compromised presentation of beta cell antigens in the pancreatic lymph nodes of juvenile animals may be the root of a first “checkpoint” in diabetes progression

Combinations of Toll-like receptor 8 agonist TL8-506 activate human tumor-derived dendritic cells

BackgroundDendritic cells (DCs) are professional antigen presenting cells that initiate immune defense to pathogens and tumor cells. Human tumors contain only few DCs that mostly display a non-activated phenotype. Hence, activation of tumor-associated DCs may improve efficacy of cancer immunotherapies. Toll-like receptor (TLR) agonists and interferons are known to promote DC maturation. However, it is unclear if DCs in human tumors respond to activation signals and which stimuli induce the optimal activation of human tumor DCs.MethodsWe first screened combinations of TLR agonists, a STING agonist and interferons (IFNs) for their ability to activate human conventional DCs (cDCs). Two combinations: TL8-506 (a TLR8 agonist)+IFN-γ and TL8-506+Poly(I:C) (a TLR3 agonist) were studied in more detail. cDC1s and cDC2s derived from cord blood stem cells, blood or patient tumor samples were stimulated with either TL8-506+IFN-γ or TL8-506+Poly(I:C). Different activation markers were analyzed by ELISA, flow cytometry, NanoString nCounter Technology or single-cell RNA-sequencing. T cell activation and migration assays were performed to assess functional consequences of cDC activation.ResultsWe show that TL8-506 synergized with IFN-γ or Poly(I:C) to induce high expression of different chemokines and cytokines including interleukin (IL)-12p70 in human cord blood and blood cDC subsets in a combination-specific manner. Importantly, both combinations induced the activation of cDC subsets in patient tumor samples ex vivo. The expression of immunostimulatory genes important for anticancer responses including CD40, IFNB1, IFNL1, IL12A and IL12B were upregulated on stimulation. Furthermore, chemokines associated with CD8$^{+}$ T cell recruitment were induced in tumor-derived cDCs in response to TL8-506 combinations. In vitro activation and migration assays confirmed that stimulated cDCs induce T cell activation and migration.ConclusionsOur data suggest that cord blood-derived and blood-derived cDCs are a good surrogate to study treatment responses in human tumor cDCs. While most cDCs in human tumors display a non-activated phenotype, TL8-506 combinations drive human tumor cDCs towards an immunostimulatory phenotype associated with Th1 responses on stimulation. Hence, TL8-506-based combinations may be promising candidates to initiate or boost antitumor responses in patients with cancer

The Vβ_\beta 17+^+ T cell repertoire: skewed Jβ\beta usage after thymic selection; dissimilar CDR3s in CD4+^+ versus CD8+^+ cells.

International audienceTo ascertain how the actual repertoire of T cell receptors (TCRs) deviates from the theoretical, we have generated a large number of junctional region sequences from TCRs carrying the V$_\beta$17 variable region. The greater than 600 sequences analyzed represent transcripts from nine different cell populations, permitting several comparisons: transcripts from an expressed vs. a non-expressed V$_\beta$17 allele, those from E$^+$ vs. E$^-$ mice, transcripts from immature vs. mature thymocytes, those from thymic vs. peripheral T cells, and those from CD4$^+$ vs. CD8$^+$ cells. These comparisons have allowed us to distinguish between the influence of molecular events involved in TCR gene rearrangement and that of various selection events that shape the T cell repertoire. Our most striking findings are: (a) that J$\beta$ usage is markedly skewed, partly due to recombination mechanics and partly due to selection forces: in particular, those mediated by the class II E molecule in the thymus; and (b) that TCRs on CD4$^+$ and CD8$^+$ cells show intriguing dissimilarities. In addition, we present evidence that N nucleotide additions occur with clear biases, probably due to idiosyncrasies of the recombination enzymes, and provide arguments that TCR and immunoglobulin CDR3s have distinct structures

Negative cross-talk between p53 and the glucocorticoid receptor and its role in neuroblastoma cells

The tumour suppressor p53 and the glucocorticoid receptor (GR) respond to different types of stress. We found that dexamethasone-activated endogenous and exogenous GR inhibit p53-dependent functions, including transactivation, up- (Bax and p21(WAF1/CIP1)) and down- (Bcl2) regulation of endogenous genes, cell cycle arrest and apoptosis. GR forms a complex with p53 in vivo, resulting in cytoplasmic sequestration of both p53 and GR. In neuroblastoma (NB) cells, cytoplasmic retention and inactivation of wild-type p53 involves GR. p53 and GR form a complex that is dissociated by GR antagonists, resulting in accumulation of p53 in the nucleus, activation of p53-responsive genes, growth arrest and apoptosis. These results suggest that molecules that efficiently disrupt GR–p53 interactions would have a therapeutic potential for the treatment of neuroblastoma and perhaps other diseases in which p53 is sequestered by GR

How Much TCR Does a T Cell Need?

International audienceKinetic features of TCR:MHC/peptide interactions dictate their outcome in vitro, some important parameters of which include the number of molecules engaged and the duration of engagement. We explored the in vivo significance of these findings in transgenic mice expressing TCRs in a quantitatively and temporally controlled manner. As anticipated, reduced TCR levels resulted in attenuated reactivity, but response thresholds were substantially lower than expected-at as low as 1/20th the normal TCR numbers and with no indication of phenotypic skewing at suboptimal levels. We also studied survival of T lymphocytes stripped of their TCRs. Unlike B cells, T cells lacking antigen receptors did not die precipitously; instead, populations decayed gradually, just as previously reported in the absence of MHC molecules