Increased IL-10-competent regulatory B cells in the decidua of early human pregnancy

Regulatory B cells (Bregs) may play a pivotal role in maintaining human pregnancy. For the first time, to the best of our knowledge, this study noted that cell percentages of CD24^hiCD38^hi Bregs and CD24^hiCD27⁺ Bregs, which can potentially produce IL-10, are increased in human decidua compared with the mid-luteal phase endometrium. In each case of decidua, the correlation between Bregs and dendritic cell (DC) or natural killer (NK) cell expression was further explored. A positive correlation between the percentage of CD24^hiCD38^hi Bregs and CD123^-CD11c⁺ myeloid DCs (mDCs) was noted. Furthermore, a significant positive correlation was also observed between the percentage of CD24^hiCD27⁺ Bregs and CD94⁺CD56^brightCD16^- suppressive NK cells. These findings regarding decidual Bregs deepen the understanding of the harmonious immunological microenvironment that sustains early human pregnancy.