Alex C Y Chen, Sneha Jaiswal, Daniela Martinez, Cansu Yerinde, Keely Ji, Velita Miranda, Megan E Fung, Sarah A Weiss, Maria Zschummel, Kazuhiro Taguchi, Christopher S Garris, Thorsten R Mempel, Nir Hacohen, Debattama R Sen <<<

The etiology and effect of age-related immune dysfunction in cancer is not completely understood. Here we show that limited priming of CD8 T cells in the aged tumor microenvironment (TME) outweighs cell-intrinsic defects in limiting tumor control. Increased tumor growth in aging is associated with reduced CD8 T cell infiltration and function. Transfer of T cells from young mice does not restore tumor control in aged mice owing to rapid induction of T cell dysfunction. Cell-extrinsic signals in the aged TME drive a tumor-infiltrating age-associated dysfunctional (T) cell state that is functionally, transcriptionally and epigenetically distinct from canonical T cell exhaustion. Altered natural killer cell-dendritic cell-CD8 T cell cross-talk in aged tumors impairs T cell priming by conventional type 1 dendritic cells and promotes T cell formation. Aged mice are thereby unable to benefit from therapeutic tumor vaccination. Critically, myeloid-targeted therapy to reinvigorate conventional type 1 dendritic cells can improve tumor control and restore CD8 T cell immunity in aging. <<<

Simona Ceglia, Alyssa Berthelette, Kelsey Howley, Yun Li, Benedikt Mortzfeld, Shakti K Bhattarai, Nicole K H Yiew, Ying Xu, Robert Brink, Jason G Cyster, Lora V Hooper, Gwendalyn J Randolph, Vanni Bucci, Andrea Reboldi <<<

Immunoglobulin A (IgA) secretion by plasma cells, terminally differentiated B cells residing in the intestinal lamina propria, assures microbiome homeostasis and protects the host against enteric infections. Exposure to diet-derived and commensal-derived signals provides immune cells with organizing cues that instruct their effector function and dynamically shape intestinal immune responses at the mucosal barrier. Recent data have described metabolic and microbial inputs controlling T cell and innate lymphoid cell activation in the gut; however, whether IgA-secreting lamina propria plasma cells are tuned by local stimuli is completely unknown. Although antibody secretion is considered to be imprinted during B cell differentiation and therefore largely unaffected by environmental changes, a rapid modulation of IgA levels in response to intestinal fluctuations might be beneficial to the host. In the present study, we showed that dietary cholesterol absorption and commensal recognition by duodenal intestinal epithelial cells lead to the production of oxysterols, evolutionarily conserved lipids with immunomodulatory functions. Using conditional cholesterol 25-hydroxylase deleter mouse line we demonstrated that 7α,25-dihydroxycholesterol from epithelial cells is critical to restrain IgA secretion against commensal- and pathogen-derived antigens in the gut. Intestinal plasma cells sense oxysterols via the chemoattractant receptor GPR183 and couple their tissue positioning with IgA secretion. Our findings revealed a new mechanism linking dietary cholesterol and humoral immune responses centered around plasma cell localization for efficient mucosal protection. <<<

An orchestrated cellular network, including adaptive lymphocytes and group 3 innate lymphoid cells (ILC3s), maintains intestinal barrier integrity and homeostasis. T cells can monitor environmental insults through constitutive circulation, scanning tissues and forming immunological contacts, a process named immunosurveillance. In contrast, the dynamics of intestinal ILC3s are unknown. Using intravital imaging, we observed that villus ILC3s were largely immotile at steady state but acquired migratory 'patrolling' attributes and enhanced cytokine expression in response to inflammation. We showed that T cells, the chemokine CCL25 and bacterial ligands regulated intestinal ILC3 behavior and that loss of patrolling behavior by interleukin-22 (IL-22)-producing ILC3s altered the intestinal barrier through increased epithelial cell death. Collectively, we identified notable differences between the behavior of ILC3s and T cells, with a prominent adaptation of intestinal ILC3s toward mucosal immunosurveillance after inflammation. <<<

Maintenance of tissue homeostasis is dependent on the communication between stem cells and supporting cells in the same niche. Regulatory T cells (T cells) are emerging as a critical component of the stem-cell niche for supporting their differentiation. How T cells sense dynamic signals in this microenvironment and communicate with stem cells is mostly unknown. In the present study, by using hair follicles (HFs) to study T cell-stem cell crosstalk, we show an unrecognized function of the steroid hormone glucocorticoid in instructing skin-resident T cells to facilitate HF stem-cell (HFSC) activation and HF regeneration. Ablation of the glucocorticoid receptor (GR) in T cells blocks hair regeneration without affecting immune homeostasis. Mechanistically, GR and Foxp3 cooperate in T cells to induce transforming growth factor β3 (TGF-β3), which activates Smad2/3 in HFSCs and facilitates HFSC proliferation. The present study identifies crosstalk between T cells and HFSCs mediated by the GR-TGF-β3 axis, highlighting a possible means of manipulating T cells to support tissue regeneration. <<<