Although the exact mechanism of suppression of D immunization by administration of passive IgG anti-D remains to be elucidated, it is known that D-positive red cells are rapidly cleared to the spleen by macrophages via IgG Fc receptor (FcγR) interactions and rendered non-immunogenic. Indeed, to ensure prophylactic anti-D is likely to be effective at preventing D immunization to a large FMH, women are tested 2–3 days later to check that fetal cells are cleared from the circulation. Otherwise, allogeneic red cells have a long survival after FMH or transfusion. Alloimmune responses are slow to develop, typically 5–15 weeks for anti-D. This is probably due to their lack of danger signals (from foreign molecules) so that they are not recognized by … Continue reading Lessons learnt from many years of experience using anti-D in humans for prevention of RhD immunization and haemolytic disease of the fetus and newborn