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

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.

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.

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.

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.