Pemphigus is an organ‐specific autoimmune bullous disease.

To determine the role of regulatory B cells (Bregs) in patients with pemphigus.

The frequency of the occurrence of CD19⁺CD24^hiCD38^hi Bregs was detected from 34 patients with pemphigus and 20 healthy controls. Interleukin (IL)‐10 secretion was processed after stimulating B cells. Specific antidesmoglein antibody (Ab) titres and their subclasses were also measured. Ab response and cytokine production from peripheral blood mononuclear cells (PBMCs) with or without Bregs were analysed.

The number of Bregs was significantly increased in patients with pemphigus compared with healthy controls (15 ± 7% vs. 9 ± 3%; P <0·01) and the proportion of Bregs in the active groups (newly diagnosed and chronic active patients) was significantly higher than in remittent individuals (16 ± 7% vs. 13 ± 8%; P =0·04). The IL‐10‐producing B cells were significantly increased upon stimulation both in patients and in healthy controls. However, the increase ratio of IL‐10‐producing B cells between short‐ and long‐term stimulation was significantly lower in patients with pemphigus (1·0‐fold vs. 2·6‐fold increase in control group; P <0·01). Strikingly, Bregs from the controls were able to suppress interferon (IFN)‐γ expression and T helper cell 1 (Th1) immune response (26% inhibition rate), while the suppressive function of Bregs from patients with pemphigus was significantly decreased (9% inhibition rate). There was no difference in Ab levels from PBMCs with or without Bregs after stimulation.

Bregs in patients with pemphigus are elevated but with defective regulatory function on Th1 cells.