CHI3L1-deficient CD4+ T cells differentiate into Th1 cells.73 Essentially, CHI3L1 is expressed in activated T cells and Th2 cells, regulating Th1 and Th2 differentiation through IFN-γ signaling via the IFN-γ–STAT1 axis.73 Therefore, CHI3L1 is a regulator of Th1 polarization and cytotoxic T lymphocyte (CTL) expression, which serve as potential therapeutic targets to enhance anti-tumor immunity. The gene discussed is CD4; the disease is neoplasm.