However, a sex-linked genetic influence and hormonal effect for females is one possible explanation.13 Females are considered to have the higher absolute number of CD4+ lymphocytes than males, and it is suggested that cytokine secretion is enhanced in the presence of estrogen.14 Moreover, androgens have been found to suppress the activity of autoimmune disease such as systemic lupus erythematosus in animal experiments.15 Gonadal steroids are likely to play important roles in modulating autoimmune diseases. The gene discussed is CD4; the disease is autoimmune disease.