What is the mechanism by which anti-Fya antibodies affect a fetus?

Anti-Fya antibodies have the potential to cross the placenta due to their IgG immunoglobulin classification. Once these antibodies cross the placental barrier, they can bind to the corresponding Fya antigen present on fetal red blood cells. This interaction can lead to the destruction of fetal red blood cells through a process called hemolysis, as antibodies can initiate immune-mediated clearance by the fetal immune system or maternal macrophages.

This mechanism is significant in the context of hemolytic disease of the fetus and newborn (HDFN), where the mother's immune system has been sensitized to the fetal red cell antigens. The destruction of fetal erythrocytes can result in anemia, jaundice, and other complications in the fetus, depending on the severity of the condition.

The other options do not accurately describe the primary mechanism of action for anti-Fya antibodies. Immediate hemolysis typically reflects a different context, sensitization of T cells does not directly relate to antibody function in this scenario, and the deposition of antibodies in the kidneys leading to renal failure is not a recognized effect of anti-Fya antibodies in the context of fetal health.