Hereditary hemochromatosis (HH) was found to affect the immune system as follows: (1) decreased number of Natural Killer T cells (NKT) relating to serum ferritin and transferrin saturation, (2) abnormalities between CD8+ T cell pool, (3) iron-related phenotypic changes in surface expression of molecules on T lymphocytes, (4) lower numbers of circulating and hepatic CD8 cells, and (5) diminished cytotoxic activities of Cytotoxic T lymphocytes (CTL) [48–50]. The gene discussed is CD8A; the disease is hereditary hemochromatosis.