About PSG5 / Pregnancy Specific Beta-1-Glycoprotein:
Pregnancy specific beta-1 glycoprotein (PSG) is a member of the carcinoembryonic antigen (CEA) family, present in the body of mammals during pregnancy. It’s most predominant during the later stages of pregnancy and plays an important role in fetal development.
PSG has a complex structure consisting of a combination of protein and carbohydrate. It contains four immunoglobulin domains. This type of protein has a similar domain structure to CEACAMs, minus a membrane anchor. It is, therefore, secreted instead. The structure can vary according to species, but all that have glycoprotein present contain a core protein covalently bound to a carbohydrate.
Pregnancy Specific Beta-1-Glycoprotein Function
PSG is essential for the healthy development of a fetus. Its functions include inducing or enhancing an immune response by regulating lymphocytes, protecting the fetus from immune attacks from the maternal bloodstream. Inflammation, infection, and trauma, can be a threat to the fetus otherwise. For this reason, the level of PSG rises in the bloodstream throughout pregnancy.
PSGs can be affected by internal and external factors. Certain viruses have been known to bind with a PSG receptor in the brain, for instance. Smoking during pregnancy may also reduce the level of PSGs in the bloodstream. If the concentration of PSG is low in the second or third trimester, this could have a detrimental effect, and has been correlated with restricted fetal growth. It can also be indicative of conditions such as Down Syndrome. Hereby, the levels of this glycoprotein are tested throughout pregnancy, particularly in the first trimester.