IN-VITRO IMMUNO-CYTOTOXICITY OF IRON EVALUATED BY DNA-SYNTHESIS OF HUMAN T-LYMPHOCYTES STIMULATED VIA CD2 AND CD3

In previous studies it was demonstrated that the in vitro exposure of human lymphocytes to iron, nickel or cobalt salts causes a significant reduction of lymphocytes expressing CD2 and CD3 surface antigens. Since both molecules are involved in T lymphocyte activation, these studies suggest that the above metals might affect T-cell activation and proliferation. Thus a method was developed for the stimulation of lymphocytes in which both CD2 and CD3 molecules were triggered simultaneously. For this purpose an anti-CD3 monoclonal antibody (mAb) was chemically bound to human erythrocytes (HE), forming HEalphaCD3 conjugates, which were used for lymphocyte stimulation. In this work the effects of iron on lymphocyte proliferation was studied, following stimulation via CD2 and CD3, in order to evaluate the immuno-cytotoxicity of iron. Increasing concentrations (5 x 10(-3) muM-10(2) muM) of iron citrate (Fe-citrate) showed that the higher concentration range (10 muM-10(2) muM) caused moderate inhibitions of lymphocyte DNA synthesis (ranging between 18.3% and 78.6%). Furthermore the presence of monocytes in culture did not interfere in the inhibitory effect of Fe-citrate. Phenotypic characterisation of DNA-synthesizing cells in the presence of Fe-citrate showed that the CD8+ (suppressor/cytotoxic) subset was the most reduced one. This study showed that iron inhibited T lymphocyte proliferation, particularly the suppressor/cytotoxic cells, suggesting that the presence of high levels of iron in in vivo situations can cause immunosuppression and, consequently, contribute to the onset of opportunistic infections and tumours.