Background: Thalassemia is a hereditary hemolytic anemia caused by mutations in the globin gene complex. Circulatory disturbances including arterial and venous thrombosis have also been noted in these patients. Aggregability of abnormal RBC and the high level of membrane-derived microparticles stemming from activated platelets and other blood cells are thought to be responsible for the associated thrombotic risk. Destruction of RBC is also thought to be an important pathophysiological consequence, particularly through the formation of circulating vesicles. To our knowledge, there has been no attempt to quantitatively evaluate the number of RBC vesicles in thalassemia. This prompted us to study the level of RBC vesicles in the peripheral blood of thalassemia patients using quantitative flow cytometry.Methods: Whole blood from each subject was doubly stained for RBC and platelet or annexin V markers, together with the known density TruCount™ beads. RBC vesicles were gated according to their forward/side scatter and RBC marker. Percentage of RBC vesicles and their absolute number were analyzed by flow cytometry.Results: Our data indicated that RBC vesicles were annexin V-positive. The number of annexin V-positive events was higher than their intact RBCs. RBC vesicles were present in both normal and thalassemic blood samples, but the numbers of RBC vesicles were significantly higher in thalassemia. Both the percentage and the absolute number of RBC vesicles were especially marked in splenectomized subjects with ␤-thalassemia/ Hemoglobin E. When clinical and hematological indices were compared with RBC vesicles, there was an inverse relationship between the degree of severity in thalassemia patients and the number of RBC vesicles.Conclusion: Flow cytometric quantitation of RBC vesicles is simple, reliable and may offer new insights in to study of the relationship between defective hemoglobin synthesis, RBC perturbation and pathophysiological complications in thalassemia.

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Infection is very common in thalassemia and is one of the major causes of death. To date, it is not quite clear why these patients are susceptible to infection. In this study, lymphocyte immunophenotyping for CD3 (T-cells), CD3 CD4 (T-helper/inducer cells), CD3 CD8 (T-suppressor/cytotoxic cells), CD3 CD19 (B-cells), and CD3 CD16/56 (natural killer cells) subsets and expression of the activation antigen CD69 on CD3 CD4 and CD3 CD8 T-cells were determined in the whole blood of thalassemia patients, using a three-color flow cytometric technique. Results showed that only splenectomized-thalassemia/hemoglobin (Hb) E patients displayed a marked increase in absolute number of all lymphocytes. In addition, splenec-tomized-thalassemia/Hb E showed a significantly lower percentage of CD3 cells, with a corresponding increase in CD19 cells. These differences, when compared with normal subjects and other thalassemia patients, may be attributed to splenectomy.-thalassemia patients, on the other hand, showed no significant difference from the normal group. While lymphocyte subsets in splenectomized-thalassemia/Hb E patients showed an abnormal distribution, T-cell activation in these patients was not different from the activation seen in normal subjects. This implies that thalassemia patients, during the steady state of disease, appear to have normal T-lymphocyte function with only moderate abnormalities of T-and B-lymphocyte subsets.

Serum concentration of iron, transferrin saturation and total iron binding capacity (TIBC) were measured on days 1, 2, 3, 5, 7, 10 and 13 in 36 Thai patients with trauma (burns excluded) to determine temporal changes in iron metabolism. Throughout the study profound hypoferraemia was observed in association with decreased transferrin saturation. TIBC, in contrast, did not differ significantly from that in controls. These findings confirm previous reports which describe altered iron metabolism in association with an adverse event, a response known as 'stress hypoferraemia', and extends these observations to non-burned patients with trauma. The degree of hypoferraemia in patients in this study was not related to sepsis, Injury Severity Score, volume of blood transfused or surgery, suggesting that hypoferraemia following trauma is an independent event. The recognition of rapid and prolonged iron sequestration provides insight into the clinical condition of patients with trauma.

Infection is very common in thalassemia and is one of the major causes of death. To date, it is not quite clear why these patients are susceptible to infection. In this study, lymphocyte immunophenotyping for CD3+ (T‐cells), CD3+CD4+ (T‐helper/inducer cells), CD3+CD8+ (T‐suppressor/cytotoxic cells), CD3−CD19+ (B‐cells), and CD3−CD16/56+ (natural killer cells) subsets and expression of the activation antigen CD69 on CD3+CD4+ and CD3+CD8+ T‐cells were determined in the whole blood of thalassemia patients, using a three‐color flow cytometric technique. Results showed that only splenectomized β‐thalassemia/hemoglobin (Hb) E patients displayed a marked increase in absolute number of all lymphocytes. In addition, splenectomized β‐thalassemia/Hb E showed a significantly lower percentage of CD3+ cells, with a corresponding increase in CD19+ cells. These differences, when compared with normal subjects and other thalassemia patients, may be attributed to splenectomy. α‐thalassemia patients, on the other hand, showed no significant difference from the normal group. While lymphocyte subsets in splenectomized β‐thalassemia/Hb E patients showed an abnormal distribution, T‐cell activation in these patients was not different from the activation seen in normal subjects. This implies that thalassemia patients, during the steady state of disease, appear to have normal T‐lymphocyte function with only moderate abnormalities of T‐ and B‐lymphocyte subsets.Cytometry (Comm. Clin. Cytometry) 42:11–17, 2000. © 2000 Wiley‐Liss, Inc.