The feature of clonal expansion of TCR Vβ repertoire, thymic recent output function and TCRζ chain expression in patients with immune thrombocytopenic purpura

Abstract

In order to identify the feature of T cells immune status in idiopathic/immune thrombocytopenic purpura (ITP) patients, TCR Vbeta repertoire, T-cell receptor (TCR) excision DNA circles (TRECs) and TCRzeta chain gene expression were examined. Reverse-transcriptase polymerase chain reaction, genescan and real-time PCR techniques were used to analyze. DNA and cDNA from peripheral blood mononuclear cells (PBMCs) of 18 ITP patients were investigated and 25 normal individuals served as control. The results showed that only 4-11 Vbeta subfamilies could be detected in each ITP case. The most frequently expressed Vbeta subfamilies were Vbeta2 and Vbeta3, while 11 Vbeta subfamilies were absent. Clonal expansion of Vbeta T cells were found in all patients. The most frequent clonal expansion T cell was Vbeta21. The number of TRECs in ITP patients (2.60 +/- 2.99 copies/1000 PBMCs) was not significant different, compared with control (3.76 +/- 3.42 copies/1000 PBMCs). The expression level of TCRzeta gene was significantly lower in ITP samples than those in control (P = 0.017). In summary, T cells in ITP patients were characterized by restricted expression of TCR Vbeta subfamilies and clonal expansion predominant in Vbeta21. The alteration of peripheral TCR Vbeta repertoire pattern may not relate to the thymic, recent output function in ITP patients. Our report is the first description of decreased TCRzeta mRNA level in the majority of ITP patients.