CD4 and carcinoma: An effective antitumor immune response demands collaboration between CD8+ and CD4+ T lymphocytes, and CD8+ cytotoxic T lymphocytes (CTL) play a central part in antitumor immunity through the production of IFN‐γ, TNF, and granzyme B following ligation of their T cell receptors (TCRs).34, 35 It has been clearly established that IFN can regulate the PD‐L1 expression in cancer cells and is the mechanism by which carcinoma cells elude being killed by immune cells.