Phenotypic characterization of circulating CD4/CD8 T-lymphocytes in β-thalassemia patients

Background: Infection is one of the most common causes of death in beta-thalassemia patients. This may be due in part to an underlying immunological abnormality. During the past decade, a subset of CD3+ T cells that express both CD4+CD8+ (DP) T-cells were discovered and have been described in several pathological conditions. However, phenotypic characterization of this unique T-lymphocyte subset in patients with beta -thalassemia has not yet been investigated. Methods: Flow cytometry was used to determine the frequency of such CD4+CD8+(DP) cells in concert with frequencies of CD4+, CD8+, NKT cells and gamma delta-TCR T-lymphocytes in the peripheral blood of beta-thalassemia/HbE patients. The frequencies of these lymphocyte subsets were compared with those in blood samples from healthy volunteers. Results: The results showed that the frequency of lymphocytes was significantly increased in splenectomized beta-thalassemia/HbE patients but the frequencies of CD3+, CD4+ and CD8+ T-lymphocytes were not significantly different among the studied groups. However, analysis of unconventional T-lymphocytes revealed a significant increase in the frequency of CD4-CD8- in splenectomized beta-thalassemia/HbE patients. The frequencies of CD4-CD8dim and CD4+CD8+ in beta-thalassemia/HbE patients were similar to the controls. Further classification of the CD4+CD8+ cells revealed that beta-thalassemia/HbE patient expressed significantly high levels of CD4brightCD8dim, with a marked increase found in non-splenectomized patients. Furthermore, significant increases in the frequency of gamma delta-TCR and NKT cells were also beta-demonstrated in these splenectomized thalassemia/HbE patients. Conclusion: Our findings show the alteration of unconventional T-lymphocyte subsets in beta-thalassemia/HbE patients, which may be responsible or may reflect the impaired immune response in beta-thalssemia disease.