Effects of rituximab and dexamethasone on regulatory and proinflammatory B‐cell subsets in patients with primary immune thrombocytopenia

Abstract Objective To investigate the cytokine production and surface marker composition of B cells in adult patients with newly diagnosed primary immune thrombocytopenia ( ITP ) before and 12 months after treatment with rituximab + dexamethasone ( RTX + DXM ) or dexamethasone ( DXM ). Methods Peripheral blood mononuclear cells were isolated from nine patients treated with RTX + DXM , seven patients treated with DXM , and seven healthy donors. Expression of the cell‐surface markers CD 5, CD 27, CD 25, and CD 19, and intracellular content of IL ‐6 and IL ‐10 were measured by flow cytometry. Results PBMC s from ITP patients at baseline contained a lower proportion of IL ‐10 + B cells ( P < .01) and IL ‐6 + B cells ( P < .01) than healthy controls. All patients responded to therapy and levels were normalized at 12 months. The proportion of CD 5 + B cells increased ( P < .01) and CD 27 + memory B cells decreased ( P < .05) 12 months after treatment with RTX + DXM compared to baseline, with an inverse correlation between platelet numbers and the proportion of CD 27 + B cells ( R = −0.71; P < .05). Conclusion Both treatment regimens normalized the frequencies of cytokine‐producing B cells. The additional increase in CD 5 + B cells after RTX + DXM is compatible with induction of Bregs.