BAFF and BAFF-R of peripheral blood and spleen mononuclear cells in idiopathic thrombocytopenic purpura

Abstract

BAFF (B-cell activating factor belonging to the TNF family) is an essential component of B-cell homeostasis, and is required for the normal survival and development of B cells. To further explore the role of this cytokine in the pathogenesis of idiopathic thrombocytopenic purpura (ITP), BAFF/BAFF-R (one of receptors of BAFF) expression levels were determined and the correlation between the clinical parameters and the BAFF expression levels was analyzed. A total of 57 patients with ITP were enrolled and 25 age and sex-matched healthy volunteers served as controls. Serum was obtained from 41 patients with ITP and 22 healthy volunteers and was analyzed with a commercial human soluble BAFF (sBAFF) ELISA kit. BAFF and BAFF-R mRNA expression of peripheral blood (PB) (n = 42) and splenocytes (SP) (n = 8) mononuclear cells (MNC) were determined by real-time quantitative PCR. The SPMNC of normal controls came from three hereditary spherocytosis patients who underwent splenectomy. The untreated patients with ITP had higher serum BAFF levels (Median 1430 pg/ml, Range: 534–5787 pg/ml) than those of normal controls (Median 1120 pg/ml, Range: 640–2376 pg/ml, p = 0.006) and treated ITP group (Median 662 pg/ml, Range 267–1265 pg/ml, p = 0.000). On the other hand, serum BAFF levels of treated patients with ITP were lower than those of normal controls (p = 0.001). There was a weak correlation (the Pearson correlation coefficient is − 0.242) between platelet count and BAFF (p = 0.064). However, BAFF levels did not correlate with platelet associated immunoglobulin or immunoglobulin levels. Moreover, the serum BAFF levels were not statistically different between acute and chronic ITP (p = 0.841). PBMNC of ITP had higher BAFF but not BAFF-R mRNA expression than that of normal controls. BAFF mRNA expression of SPMNC had a positive correlation with BAFF-R in ITP patients but not in PBMNC of normal controls and untreated ITP patients. The BAFF-R mRNA expression of SPMNC was shown to be 15.29 times higher than that of PBMNC in ITP. BAFF might contribute to autoimmunity and disease development in ITP. However, BAFF serum level must be carefully considered as a surrogate marker of disease activity in ITP.

• Idiopathic thrombocytopenic purpura
• BAFF
• BAFF-R
• spleen
• peripheral blood

Acknowledgements

This project was supported in part by grants of National Natural Science Foundation of China (30670900). Ministry of Education of China (20060023031), Ministry of Personnel of China (2006), Ministry of Health (200802031) and Tianjin Key Project for Basic Research (06YFJZJC01800). The authors would like to thank Prof. Man-Chiu Poon (University of Calgary, Canada) for critical review of the manuscript.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.