Which antibody class is known for its ability to cross the placenta?

The ability of an antibody class to cross the placenta is a unique feature of IgG antibodies. This class plays a significant role in providing passive immunity to the fetus during pregnancy. As the fetus develops, IgG is transported from the mother’s bloodstream through the placenta, which helps protect the unborn child from infections by providing them with maternal antibodies.

IgA is primarily found in mucosal areas as well as in secretions like saliva, tears, and breast milk, but it does not cross the placenta. IgE is mainly involved in allergic reactions and responses to parasitic infections and is also not known for crossing the placenta. IgM, which is the first antibody produced in response to an infection, is primarily present in the blood and does not cross the placenta due to its large size. Therefore, the unique characteristic of IgG in crossing the placenta makes it crucial for fetal immunity.