In NSCLC, MHC‐II expression is suppressed by histone deacetylases (HDACs) and phosphorylated extracellular signal‐regulated kinase (ERK), limiting CD4+ T‐cell activation and intratumoral immune cell recruitment, potentially explaining resistance to immune checkpoint inhibitors in tumours with low MHC‐II expression. This evidence concerns the gene CD4 and neoplasm.