Human CD24+CD38+ regulatory B cells promote Pro-resolving Macrophage Function through the synergistic effect of IL-10 and PD-L1

Abstract Regulatory B cells (Bregs), specifically the CD24⁺CD38⁺ phenotype, are known for their capacity to reduce inflammation by releasing interleukin 10(IL-10). However, their potential role in regulating inflammation through macrophage differentiation is not well understood. This study investigates how CD24⁺CD38⁺ regulatory B cells modulate the differentiation and function of pro-resolving macrophages through programmed death-ligand 1 (PD-L1)/programmed death-1 (PD-1) interactions and IL-10 secretion. Human CD24⁺CD38⁺ B cells were isolated from peripheral blood and co-cultured with THP-1-derived macrophages. Recombinant IL-10/PD-L1 and neutralizing antibodies were used to conduct gain and loss-of-function studies. Flow cytometry, quantitative PCR, and mass spectrometry were used to evaluate macrophage polarization, efferocytosis activity, and pro-resolving lipid mediator production. After co-culture, M2 polarization, PD-1 expression, and efferocytosis activity were increased significantly. Inhibition of either IL-10 or PD-L1 pathway reduced M2 macrophage differentiation and functional activity. Co-culture of macrophages with CD24⁺CD38⁺ B cells enhanced the production of pro-resolving lipid mediators, particularly 12-HEPE and RvD5 through IL-10 secretion and PD-L1/PD-1 ligation. These findings reveal a novel mechanism by which human CD24⁺CD38⁺ regulatory B cells promote macrophage-mediated resolution of inflammation through IL-10 secretion and PD-L1/PD-1 ligation. By exploring how these regulatory pathways influence macrophage biology, we ultimately aim to uncover novel therapeutic targets for enhancing inflammation resolution in chronic inflammatory diseases.