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

BACKGROUND: Infection is one of the most common causes of death in β-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 β-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 γδ-TCR T-lymphocytes in the peripheral blood of β-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 β-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 β-thalassemia/HbE patients. The frequencies of CD4-CD8dim and CD4+CD8+ in β-thalassemia/HbE patients were similar to the controls. Further classification of the CD4+CD8+ cells revealed that β-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 γδ-TCR and NKT cells were also demonstrated in these splenectomized β-thalassemia/HbE patients.

CONCLUSION: Our findings show the alteration of unconventional T-lymphocyte subsets in β-thalassemia/HbE patients, which may be responsible or may reflect the impaired immune response in β-thalssemia disease.