IgG4 production is confined to human IL-10-producing regulatory B cells that suppress antigen-specific immune responses

Background: IL-10-producing regulatory B cells suppress immune responses, and lack of these cells leads to exacerbated symptoms in mouse models of chronic inflammation, transplantation, and chronic infection. IgG(4) is a blocking antibody isotype with anti-inflammatory potential that is induced in human high-dose antigen tolerance models. Objective: We sought to characterize human inducible IL-10-secreting B regulatory 1 (B(R)1) cells and to investigate their immunoregulatory capacity through suppression of cellular immune responses and production of anti-inflammatory immunoglobulins. Methods: Highly purified IL-10-secreting B cells were phenotypically and functionally characterized by means of whole-genome expression analysis, flow cytometry, suppression assay, and antibody production. B cells specific for the major bee venom allergen phospholipase A(2) (PLA) were isolated from beekeepers who displayed tolerance to bee venom antigens and allergic patients before and after specific immunotherapy. Results: Human IL-10(+) B(R)1 cells expressed high surface CD25 and CD71 and low CD73 levels. Sorting of CD73(-)CD25(+)CD71(+) B cells allowed enrichment of human B(R)1 cells, which produced high levels of IL-10 and potently suppressed antigen-specific CD4(+) T-cell proliferation. IgG(4) was selectively confined to human B(R)1 cells. B cells specific for the major bee venom allergen PLA isolated from nonallergic beekeepers show increased expression of IL-10 and IgG(4). Furthermore, the frequency of IL-10(+) PLA-specific B cells increased in allergic patients receiving allergen-specific immunotherapy. Conclusion: Our data show the characterization of IL-10(+) B(R)1 cells and in vivo evidence for 2 essential features of allergen tolerance: the suppressive B cells and IgG(4)-expressing B cells that are confined to IL-10(+) B(R)1 cells in human subjects. (J Allergy Clin Immunol 2013;131:1204-12.)