The role of B cells in pregnancy: the good and the bad.

B lymphocytes are pleiotropic cells belonging to the adaptive arm of the immune system. Although B cells were classically regarded for their capacity to produce antibodies, in the recent years, several other functions were attributed to these cells. B cells can uptake, process and present antigens as well as produce several cytokines that further influence immunity.Mammalian pregnancies represent a fascinating phenomenon in which the maternal immune system must be able to 'tolerate' the semi-allogenic fetus while simultaneously protecting the mother and the fetus against external pathogens. This requires a finely regulated balance between immune activation and tolerance. In this regard, B cells and the antibodies they produced were shown to actively participate in both, pregnancy well-being as well as pregnancy-associated pathologies.We discuss here the currently available information concerning the role of B cells in the context of pregnancy.