Pulsed high-dose dexamethasone improves interleukin 10 secretion by CD5+ B cells in patients with primary immune thrombocytopenia.

Background: B cells expressing CD5 are potentially capable of producing interleukin 10 (IL-10) which contributes to the regulatory function of B cells. This study was aimed at exploring the alteration of numbers of CD5(+) B cells and their ability of producing IL-10 in patients with immune thrombocytopenia (ITP), and the effects of pulsed high-dose dexamethasone (HD-DXM) therapy on CD5(+) B cells.

Methods: Peripheral blood mononuclear cells from 25 adult ITP patients were stained with PE-CD5/FITC-CD19 antibodies for flow cytometry analyses before and after HD-DXM therapy. The expression of IL-10 mRNA was measured by RT-PCR. After 24 h culture with or without dexamethasone in the presence of PMA, ionomycin and Brefeldin A, cells were permeabilized and stained with APC-IL-10 antibody to investigate intracellular IL-10 expression. Supernatant IL-10 concentration was detected by ELISA.

Results: The number of CD5(+) B cells was elevated in patients with ITP. Expression of IL-10 mRNA, percentage of IL-10(+) cells and intracellular IL-10 in CD5(+) B cells from untreated patients were significantly higher than that in controls. In contrast, ITP patients showed lower IL-10 concentration in supernatants than controls. After HD-DXM therapy, the number of CD5(+) B cells decreased to normal level, while intracellular IL-10 expression in CD5(+) B cells was further enhanced and IL-10 concentration in supernatants was also increased. Similar results were observed when dexamethasone was administrated in vitro.

Conclusions: Increased number of CD5(+) B cells in which IL-10 is accumulated with decreased IL-10 concentration in supernatants suggests that the ability of CD5(+) B cells to secret IL-10 is impaired in ITP patients. Both the aberrant number and ability of IL-10 secretion of CD5(+) B cells could be corrected by HD-DXM.