Under normal physiological conditions, an immunosuppressive environment is formed in and around HFs, which can effectively inhibit the infiltration of T lymphocyte subsets at HF by downregulating the expression of histocompatibility complex (MHC) class I molecules in the HFs, inhibiting the surface molecules required to present self-antigens to NK cells, including CD8+ T lymphocytes. The gene discussed is CD8A; the disease is Hand-foot syndrome.