This study focused on the tight junction protein CLDN18.2, which is predominantly expressed in most G/GEJ adenocarcinomas and manifests potential for precise detection and treatment.[6] Through the examination of CLDN18.2 expression, prognosis, and clinical features in GC within cohorts from both PKUCH and TCGA, we confirmed 54.4% CLDN18.2‐positive GCs, associated with poor prognosis in early stages, negatively correlated with PD‐L1, CD3 and CD4, and closely linked to suppressed TIME. The gene discussed is CD4; the disease is gastric cancer.