CD8A and neoplasm: Along similar lines, L johnsonii in collaboration with C. sporogenes converts dietary tryptophan to Indole-3-propionic acid that promotes the infiltration of CD8+ T cells into tumor sites and enhances the H3K27 acetylation in the Tcf7 gene thereby modulating the stemness of these cells and facilitating the generation of progenitor exhausted CD8+ T cells (Tpex) subsequently ameliorating the efficacy of anti-PD-1 immunotherapy (Jia et al., 2024b).