Which antibody can cross the placenta and attach to infant cells?

The correct answer indicates that maternal antibodies, specifically anti-A and anti-B, can cross the placenta and attach to infant cells. This can occur because these immunoglobulins are of the IgG class, which is small enough to pass through the placental barrier.

During pregnancy, IgG antibodies from the mother can be transferred to the fetus, providing passive immunity. Maternal anti-A and anti-B antibodies result from the mother's blood type; for example, a mother with type O blood can produce both anti-A and anti-B antibodies. If the infant has type A or B blood, this can lead to hemolytic disease of the newborn (HDN) if these antibodies attack the infant's red blood cells.

In contrast, other antibodies listed, such as maternal anti-D and anti-K, may not cross the placenta or may not have the same implications during pregnancy. Maternal anti-D is associated with Rh incompatibility but does not attach to infant cells in the same way during gestation. Furthermore, anti-K (anti-Kell) is typically not present in significant amounts that would lead to serious clinical issues as with anti-A and anti-B in the case of ABO incompatibility.

Understanding the ability of specific antibodies to cross the placenta helps