T cells involved in tumor immunity include MHC class I antigen-restricted CD8+ cytotoxic T lymphocyte (CTL), MHC class II antigen-restricted CD4+ helper T cell (TH), tumor-promoting Tregs and etc. T cells are capable of sensing extracellular lactate levels, which elicits intracellular adjustments in signaling, cellular function, and homeostasis of the internal environment. The gene discussed is CD4; the disease is neoplasm.