We evaluated phagocytic and lytic activities of peripheral blood monocytes (PBMo) from patients with thalassemia major (ThP) using C pseudotropicalis as the target. PBMo from ThP showed decreased lytic activity (P less than .001), whereas the phagocytic activity did not differ from that of the controls. Significant inverse correlations were found between lytic activity of PBMo and age of patients (r2 = .47; P less than .01) and also between lytic activity and serum ferritin levels (r2 = .65; P less than .001). No association was found between lytic activity and other variables (blood transfusion regimens, therapy with desferrioxamine, liver damage, and the presence of sHBAg). Splenectomy showed no positive effect on PBMo functions from ThP. Our results suggest that PBMo from ThP have an intracellular defect in their microbicidal mechanisms associated with iron overload. This cell dysfunction could be responsible, at least in part, for the increased susceptibility to infections reported in ThP.

We evaluated phagocytic and lytic activities of peripheral blood monocytes (PBMo) from patients with thalassemia major (ThP) using C pseudotropicalis as the target. PBMo from ThP showed decreased lytic activity (P less than .001), whereas the phagocytic activity did not differ from that of the controls. Significant inverse correlations were found between lytic activity of PBMo and age of patients (r2 = .47; P less than .01) and also between lytic activity and serum ferritin levels (r2 = .65; P less than .001). No association was found between lytic activity and other variables (blood transfusion regimens, therapy with desferrioxamine, liver damage, and the presence of sHBAg). Splenectomy showed no positive effect on PBMo functions from ThP. Our results suggest that PBMo from ThP have an intracellular defect in their microbicidal mechanisms associated with iron overload. This cell dysfunction could be responsible, at least in part, for the increased susceptibility to infections reported in ThP.

To evaluate whether indomethacin (IM) and thymostimulin (TP-1) could revert the alterations of natural killer cytotoxicity (NKC) observed in patients and carriers of Thalassemia Major (TM), 14 TM patients, 10 TM carriers, 16 normal controls, and 4 polytransfused patients were studied. In vitro, IM induced an increase in NKC of normal controls and TM carriers (Δ CI: + 5.98±2.49 and + 9.77±6.82 respectively), but not in TM patients (-0.32±1.45) or other polytransfused recipients. The addition of IM to Concanavalin A (Con A) also resulted in an increase of NKC in normal controls and TM carriers, similar to that induced by each substance separately in normal controls, or by IM alone in TM carriers. Similarly, TP-1 (50 μg/ml) induced increases of NKC in normal subjects (+ 4.66±3.62), but not in TM patients (-1.1±2.43). The impairment in NKC observed in TM and polytransfused patients, and the absence of response to Con A in both, TM patients and carriers, do not seem to be mediated by an excessive production of prostaglandins. The lack of response not only to Con A, but also to TP-1 could indicate a quantitative or qualitative defect in T cells, that affects NKC regulation, or a deficient response of NK cells to modulators produced by T lymphocytes.