Microbiology Practice Exam

The immunoglobulin that can pass through the placenta to provide immunity to a fetus is IgG. This is the most abundant antibody in the bloodstream and plays a crucial role in the immune response.

During pregnancy, IgG is actively transferred from the mother to the fetus via the placenta, which provides the developing fetus with passive immunity against pathogens that the mother has encountered. This transfer of IgG is vital because it gives the newborn immediate protection during the first months of life when its own immune system is still maturing.

In contrast, IgA primarily protects mucosal surfaces and is passed to infants through breast milk rather than the placenta. IgM, which is the first antibody produced in response to an infection, cannot cross the placenta due to its larger size and structural properties. IgE is mainly involved in allergic reactions and defense against parasitic infections and does not have a significant role in fetal immunity through placental transfer. Each of these immunoglobulins has specific functions and locations in the immune system, but only IgG is designed to provide transplacental immunity.