Effect of transfusional iron overload on immune response

Increased susceptibility to infectious disease is observed in persons with transfusion-dependent thalassemia and iron overload who experience increase d exposure to pathogens and chronic immune stimulation. An abnormal low CD8 (+) T (LT8) immune phenotype defines a subgroup of patients. The CD8(+) T c ell immunophenotype is stable despite continued blood transfusion and is in dependent of age. CD8(+) T cells, but not CD4(+) T cells, were modulated du ring intravenous chelation with deferoxamine. Return to characteristic pret reatment levels of CD8 was observed in both the low and the normal groups, suggesting the possibility of a set point. Proliferative response to mitoge ns and antigens was increased by chelation. Because CD8(+) T cells are impo rtant in immune response to infectious disease, these studies suggest that intrinsic CD8(+) T cell subset differences may be a critical factor in dete rmining susceptibility to infection independent of transfusional iron overl oad or alloantigen exposure.