B cells acquire a unique and differential transcriptomic profile during pregnancy.

Pregnancy alters B cell development and function. B cell activation is initiated by antigens binding to the BCR leading to B cell survival, proliferation, antigen presentation and antibody production. We performed a genome-wide transcriptome profiling of splenic B cells from pregnant (P) and non-pregnant (NP) mice and identified 1136 genes exhibiting differential expression in B cells from P mice (625 up- and 511 down-regulated) compared to NP animals. In silico analysis showed that B cell activation through BCR seems to be lowered during pregnancy. RT-qPCR analysis confirmed these data. Additionally, B cells from pregnant women stimulated in vitro through BCR produced lower levels of inflammatory cytokines compared to non-pregnant women. Our results suggest that B cells acquire a state of hypo-responsiveness during gestation, probably as part of the maternal immune strategy for fetal tolerance but also open new avenues to understand why pregnant women are at highest risk for infections.