T lymphocytes subsets in experimental iron overload.

Several abnormalities of the immune system have been reported in association with clinical and experimental iron overload. To dissect further such abnormalities, changes in lymphocyte subsets were evaluated in iron-loaded male Sprague-Dawley rats. The iron-loading protocol consisted of a total dose of irondextran (1.5 mg/Kg body weight) divided in daily intramuscular injections over twenty consecutive days. At days 0, 20, and 50 after initiation of iron injections lymphocyte subsets in blood, spleen and mesenteric lymph nodes were estimated by indirect immunofluorescence using monoclonal antibodies recognizing T cells (W3.13), the subset of helper T cells in (W3.25), and the subset of cytotoxic T cells (OX.8). By day 20, there was no change in the number of W3.25+ T cells in the blood of iron-loaded animals as compared to the controls, but the OX.8+ T cells were significantly elevated. At this time, the ratio W3.25 +/OX.8+ cells was significantly decreased (0.5 in experimental rats vs 2.0 in controls). Similar results were obtained at day 50. In the spleen, there was a decrease in the proportion of W3.25 +T cells and an increase in OX.8+ T cells at day 20. However, these values returned to normal by day 50. A negative correlation between W3.25 +/OX.8+ ratio and serum ferritin was observed in blood and spleen during iron administration. These changes were associated with abnormalities in lymphocyte proliferative response. No changes in W3.25 +/OX.8+ ratio were observed in mesenteric lymph nodes. These results demonstrate that iron overload alters the distribution of T lymphocytes in various compartments of the immune system.