CD4 and Tangier disease: Patients with iron-overload in beta-thalassemia major have decreased CD4+ T cells but increased CD8+ T cell numbers (Porto and De Sousa, 2007), while patients suffering from hereditary hemochromatosis (HH) have apparently normal CD4+ and reduced CD8+ numbers, with the latter displaying a more “effector” phenotype, suggesting again that increased intracellular iron availability may have hyper-proliferative effects in T cells, although this may well-depend on which oxidation form of Fe is available (Costa et al., 2015).