PRF1 and colonic neoplasm: The antitumor effect for colon cancer mediated by Vδ1 T cells could be achieved not only by the secretion of cytokines (CD107a, perforin, granzyme B), but also by the direct contact between cells and the cytotoxicity-related receptors and ligands (Fas, death receptor 4/5, MICA/B, and ICAM-1) (47).