Lymphocyte subsets and specific T-cell immune response in thalassemia

Abstract

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.

Activated peripheral blood and endothelial cells in thalassemia patients

“…Although some investigators have not found differences in the activation status of peripheral blood lymphocytes [3,4,5,6,7], our results clearly show that our patients, with transfusion-dependent thalassemia, have increased numbers of activated peripheral blood cells. The majority of our patients have received more than 50 blood units throughout their life, and no correlation was found between the activation status and the number of transfusions.…”

“…In another report, the levels of sICAM predicted graft rejection in transplanted thalassemics [14]. The reason(s) for this phenomenon is not well investigated, but iron overload, transfusions, infectious agents, red blood cell (RBC) rheological properties, and factors derived from increased RBC destruction may play a significant role [1,4,7,8,9,22].…”

“…It is known that thalassemia patients suffer from immunomodulation, including alterations in lymphocyte subsets, abnormal levels of cytokines, and the presence of alloantibodies [1,2,3,4,5,6,7]. It has been reported that thalassemia children have decreased levels of natural killer cells and increased activation of the expression of interleukin (IL) 2 receptor (CD25), HLA-DR, and CD45RO on lymphocytes [7,8,9].…”

“…Frequent antigenic stimuli through blood transfusions, viral and bacterial infections, and iron overload have been reported [1,4,7,8,9,21]. As a consequence of endothelial cell activation, blood cells (monocytes, neutrophils, T lymphocytes) adhere and migrate through the endothelium into the tissues [12,23,24,25,26].…”

Thalassaemia major and infectious risk: High Mobility Group Box‐1 represents a novel diagnostic and prognostic biomarker

“…Besides predisposing to infections by encapsulated bacteria, splenectomy has also been correlated with immune system modifications, including quantitative lymphocyte changes without any functional impairment, as well as aggravation of the immunological effects of multiple transfusions, due to the reduced immune clearance (Pattanapanyasat et al, 2000).…”