How immune mechanisms are affected by pregnancy.

Pregnancy requires physiologic adaptations in all maternal systems, including the immune system. This process is complex and includes modifications at different levels and compartments of the maternal immune system. Although many of these changes are only partially explored and understood, recent investigations have showed that during pregnancy maternal circulating immune cells undergo modifications in cell counts, phenotypes, functions and ability to produce soluble factors, such as cytokines. The ultimate goal is to establish and maintain a successful pregnancy, which involves a state of selective immune tolerance, immunosuppression and immunomodulation in the presence of a strong anti-microbial immunity. The mammalian immune system has evolved to coexist with these needs by down-regulating potentially dangerous T-cell-mediated immune responses, while activating certain components of the innate immune system, such as monocytes and neutrophils. This unique dysregulation between different components of the immune system plays a central role in the maternal adaptation to pregnancy.