OBJECTIVETo investigate the roles of B-lymphocyte stimulator/ a proliferation-inducing ligand (BLyS/April) in immunological pathogenesis of idiopathic thrombocytopenic purpura (ITP).

METHODSThirty ITP children and 30 age-matched healthy children were studied. Reverse-transcription PCR (RT-PCR) and real-time PCR were used to evaluate the mRNA levels of BLyS/ April, receptors for BLyS/April (BR3, BCMA and TACI) and cytokines in ITP patients. Flow cytometry was performed to measure relative mean fluorescence intensity (relative MFI) for platelet-associated immunoglobulin G (PAIgG).

RESULTS(1) The transcription levels of BLyS/April in monocytes/macrophage [(8.30 +/- 2.31) x 10(-1) and (7.51 +/- 1.93) x 10(-3), respectively] were significantly up-regulated in acute ITP compared with that in healthy controls [(3.95 +/- 1.04) x 10(-1) and (3.08 +/- 0.82) x 10(-3), respectively] (P < 0.0.1). (2) Expression levels of the BLyS/April receptors BR3, BCMA and TACI mRNA were remarkably raised during acute phase of ITP (P < 0.01). (3) The mRNA levels of cytokines, including IL-4, IL-5, IL-6, IL-10 and IL-15, were significantly higher in acute phase ITP than in healthy controls (P < 0.01). (4) The mRNA levels of IL-10 and IFN-alpha were significantly elevated in acute phase of ITP. (5) Relative MFI of acute phase ITP patients (67.4 +/- 28.1) was higher than that in healthy controls (19.5 +/- 8.5) (P < 0.01), and there was a significant positive correlation between relative MFI and BLyS/April as well as their receptors (BR3, BCMA and TACI) (r = 0.56, 0.53, 0.62, 0.70, 0.45, respectively, P < 0.01), relative MFI in ITP patients decreased after treatment.

CONCLUSIONOver-expression of BLyS/April may be one of factors contributed to the immunological dysfunction in ITP.