[Impaired interleukin-10 secretion by CD5(+) B cells in patients with primary immune thrombocytopenia]

To investigate the number of peripheral blood CD5(+) B cells and their ability of secreting IL-10 in patients with immune thrombocytopenia (ITP).

Peripheral blood lymphocytes were isolated from 57 pre-treated, 40 post-treated ITP patients and 25 controls using Ficoll-Hypaque density centrifugation and then stained with PE-CD5/FITC-CD19 for flow cytometric analysis. After 24-hour culture, lymphocytes were stained with APC-IL-10 for intracellular cytokine detection. ELISA assay was employed to determine IL-10 concentration in supernatants.

The percentage and absolute number of CD5(+) B cells in peripheral blood from pre-treated ITP patients were significantly higher than that from normal controls (3.75 ± 2.37)% vs (2.10 ± 1.08)%, P < 0.01; (6.29 ± 5.77)× 10(7)/L vs (3.06 ± 1.90)× 10(7)/L, P < 0.01. CD5(+) B cells expressed more intracellular IL-10 than other lymphocyte subsets both in ITP patients and normal controls. The percentages of IL-10(+) cells within CD5(+) B cells in pre-treated ITP patients and normal controls were (29.51 ± 20.73)% and(15.90 ± 9.58)%, respectively(P < 0.01). Intracellular mean fluorescence intensity (MFI) of IL-10 in CD5(+) B cells was 27.95 ± 13.99 in pre-treated patients, which was significantly higher than that in controls (P < 0.01). In contrast, IL-10 concentration in supernatants was (173.05 ± 102.50) ng/L in pre-treated ITP group, which was lower than that (230.61 ± 76.96) ng/L in controls. In patients who achieved remission, the number of CD5(+) B cells decreased to level comparable to normal controls. While intracellular IL-10 MFI of CD5(+) B cells in post-treated ITP patients remained as high as in pre-treated ones, the IL-10 concentration in supernatants increased to level similar to controls.

The significantly increased number of CD5(+) B cells and accumulated IL-10 in CD5(+) B cells suggested impaired IL-10 secretion in ITP patients. The number and the ability of secreting IL-10 of CD5(+) B cells could be restored after effective treatments in patients with ITP.