IL‐10 produced by activated human B cells regulates CD4+ T‐cell activation in vitro

Abstract

IL‐10‐producing regulatory B cells have been identified in mice and shown to downregulate inflammation, making them potentially important for maintenance of tolerance. In this study, we isolated B cells from human blood and spleen, and showed that after a short period of ex vivo stimulation a number of these cells produced IL‐10. The IL‐10‐producing B cells did not fall within a single clearly defined subpopulation, but were enriched in both the memory (CD27⁺) and the transitional (CD38^high) B‐cell compartments. Combined CpG‐B+anti‐Ig stimulation was the most potent IL‐10 stimulus tested. B cells stimulated in this way inhibited CD4⁺CD25⁻ T‐cell proliferation in vitro by a partially IL‐10‐dependent mechanism. These findings imply that manipulating IL‐10 production by human B cells could be a useful therapeutic strategy for modulating immune responses in humans.