How do antibodies to the Rh antigen differ from ABO antibodies?

1. ABO antibodies are preformed, present without any prior exposure to incompatible blood. 2. Rh antibodies behave like antibodies elsewhere in the body: exposure comes first, then production. 3. They are produced only in Rh negative individuals, and only after they meet the Rh antigen. 4. That first meeting is called sensitisation, and it follows an incompatible transfusion or the birth of an Rh positive baby to an Rh negative mother. 5. Rh positive people already carry the antigen as self, so they do not make antibodies against it. 6. Anti-Rh antibodies do cross the placenta, which is precisely the mechanism of hemolytic disease of the newborn, so the last option is false and clinically important. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 18 "The Cardiovascular System: Blood", section 18.6 Blood Typing_