OBJECTIVETo explore the characteristics of B cell-activating factor (BAFF) secreted by peripheral blood monocyte-derived dendritic cell (MoDC) in chronic idiopathic thrombocytopenic purpura (cITP) and the function of MoDC on B cell proliferation.

METHODSTen cITP patients were studied dynamically before and after treatment. The BAFF levels in serum and the supernatant of LPS stimulated MoDC were tested with ELISA. The BAFF gene expression in LPS stimulated MoDC was tested with RQ-PCR, the B cell proliferation co-cultured with the supernatant of LPS stimulated MoDC for 5 days was tested with flow cytometry for CFSE and (3)H thymidine incorporation.

RESULTSThe BAFF level in serum (serum BAFF) \[(2461 ± 483) ng/L\], and supernatant of LPS stimulated MoDC (supernatant BAFF) \[(1113 ± 113) ng/L\] and BAFF mRNA in LPS stimulated MoDC (BAFF mRNA) (1.70 ± 0.23) before treatment were higher than that after treatment \[(621 ± 53) ng/L, (490 ± 49) ng/L and 0.37 ± 0.12\] and normal group \[(742 ± 77) ng/L, (582 ± 63) ng/L and 0.52 ± 0.08\]. There was a positive correlation among serum BAFF, supernatant BAFF and BAFF mRNA, and a negative correlation among serum BAFF, supernatant BAFF and BAFF mRNA and blood platelet count (BPC) in all ITP patients. The supernatant of LPS-stimulated MoDC from untreated patients enhanced B cell proliferation as compared with the supernatant of LPS-stimulated MoDC from treated patients and normal group.

CONCLUSIONBAFF might contribute to disease development in cITP. MoDC may directly increase B cell proliferation by secreting BAFF without T cell help, playing an important role in the antibody production in cITP.