The expression profile of toll-like receptor signaling molecules in CD19(+) B cells from patients with primary immune thrombocytopenia.

Background: B cells play a critical role in the pathogenesis of immune thrombocytopenia (ITP), and toll-like receptor (TLR) signaling is essential for the activation of autoreactive B cells. The objective of this study was to investigate the expression profile of TLR signaling molecules in circulating and splenic CD19(+) B cells isolated from ITP patients.

Methods: CD19(+) B cells were magnetically isolated from peripheral blood and splenocytes. Human Toll-Like Receptor Signaling Pathway RT(2) Profiler™ PCR Array was used to determine the differences in mRNA expression of 84 TLR signaling pathway genes between ITP patients and controls. Flow cytometry was used to investigate intracellular expression of cytokines (IL-1β and IL-10).

Results: A total of 31 genes involving TLR signaling pathways were differentially transcribed in circulating CD19(+) B cells, among which 27 were up-regulated in ITP. By comparison, differentially transcribed genes amounted to 39 in splenic B cells in ITP, among which only two were down-regulated. Up to 18 TLR signaling molecules exhibited up-regulated transcriptional levels both in splenic B cells and in circulating B cells in ITP. However, Only IL-10 and IL-1β were significantly upregulated in both the circulating and splenic B cells of patients with ITP. Intracellular staining of IL-10 and IL-1β confirmed the results of PCR Array.

Conclusions: The expression of TLRs and downstream cytokines, including IL-10 and IL-1β, is up-regulated in circulating and splenic B cells in ITP patients, suggesting that activated TLR signaling pathways in B cells may play dual roles in the pathophysiology of primary ITP.