CD4+ T cells are key components of the immune response during lung infections and can mediate protection against tuberculosis (TB) or influenza. However, CD4+ T cells can also promote lung pathology during these infections, making it unclear how these cells control such discrepant effects. Using mouse models of hypervirulent TB and influenza, we observed that exaggerated accumulation of parenchymal CD4+ T cells promotes lung damage. Low numbers of lung CD4+ T cells, in contrast, are sufficient to protect against hypervirulent TB. In both situations, lung CD4+ T cell accumulation is mediated by CD4+ T cell-specific expression of the extracellular ATP (eATP) receptor P2RX7. P2RX7 upregulation in lung CD4+ T cells promotes expression of the chemokine receptor CXCR3 and favors in situ proliferation. Our findings suggest that direct sensing of lung eATP by CD4+ T cells is critical to induce tissue CD4+ T cell accumulation and pathology during lung infections.
Sensing of extracellular metabolites controls CD8+ T cell function. Their accumulation can occur through export by specialized molecules, such as the release channel Pannexin-1 (Panx1). Whether Panx1 controls CD8+ T cell immune responses to antigen, however, has not been previously addressed. Here, we report that T cell-specific Panx1 is needed for CD8+ T cell responses to viral infections and cancer. We found that CD8-specific Panx1 favors memory CD8+ T cell survival primarily through ATP export and induction of mitochondrial metabolism. CD8-specific Panx1 is also crucial for the effector expansion of CD8+ T cells, however this regulation occurs independently of eATP. Instead, our results suggest a connection between Panx1-induced extracellular lactate accumulation and the complete activation of effector CD8+ T cells. In summary, Panx1 regulates effector and memory CD8+ T cells through export of distinct metabolites and by engaging different metabolic and signaling pathways.
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