CD8A and neoplasm: This decreases, in turn, further limits the antitumor efficacy of the CAR T‐cells and their ability to infiltrate tumor sites.[21, 39, 40, 41] In a recent study, butyrate and propionate were shown to restrict the antitumor effects of T‐cells by affecting several key mechanisms related to immune activation and T‐cell functionality.[20, 29] Butyrate restrained the induction of tumor‐specific CD8+ T‐cells.