Project description:Tissue and microbial cues regulate the abundance and function of CD8+ T cells at barrier sites, yet the impact of specific microbes on their long-term durability remains unclear. Here, we show that the commensal protist Tritrichomonas musculus (T. mu) depletes intestinal CD8+ T cells, particularly tissue resident memory (TRM) cells, through activation of localized type 2 immunity. Colonization with T. mu or administration of its major secreted metabolite, succinate, led to the rapid decline of intestinal CD8+ T cells but left systemic memory T cells unaffected. The purinergic receptor, P2RX7, is highly expressed by intestinal TRMs and chemical antagonism of this receptor markedly restored CD8+ T cells during succinate feeding. Using lymphocytic choriomeningitis virus (LCMV) infection to track antigen-specific CD8+ memory T cells, we found viral-specific CD8+ TRMs repopulate the intestine independent of LCMV reinfection after removal of succinate treatment. These findings highlight how commensal protists and their metabolites reset homeostatic CD8+ T cell carrying capacity through damage-independent stimulation of TRM apoptosis and regulate mucosal memory.
