Regulatory B cells have been identified that strongly reduce allergic and auto‐immune inflammation in experimental models by producing IL‐10. Recently, several human regulatory B‐cell subsets with an impaired function in auto‐immunity have been described, but there is no information on regulatory B cells in allergic asthma.

In this study, the frequency and function of IL‐10 producing B‐cell subsets in allergic asthma were investigated.

Isolated peripheral blood B cells from 13 patients with allergic asthma and matched healthy controls were analyzed for the expression of different regulatory B‐cell markers. Next, the B cells were activated by lipopolysaccharide (LPS), CpG or through the B‐cell receptor, followed by co‐culture with endogenous memory CD4⁺ T cells and house dust mite allergen DerP1.

Lower number of IL‐10 producing B cells were found in patients in response to LPS, however, this was not the case when B cells were activated through the B‐cell receptor or by CpG. Further dissection showed that only the CD24^hiCD27⁺ B‐cell subset was reduced in number and IL‐10 production to LPS. In response to DerP1, CD4⁺ T cells from patients co‐cultured with LPS‐primed total B cells produced less IL‐10 compared to similar cultures from controls. These results are in line with the finding that sorted CD24^hiCD27⁺ B cells are responsible for the induction of IL‐10⁺ CD4⁺ T cells.

Taken together, these data indicate that CD24^hiCD27⁺ B cells from allergic asthma patients produce less IL‐10 in response to LPS leading to a weaker IL‐10 induction in T cells in response to DerP1, which may play a role in allergic asthma.