Failure of anti-D prevention in monozygotic twins.

Abstract

The injection of anti-D into Rh-negative subjects who have Rh-positive red cells in the circulation results in the inhibition of immunization against the D-antigen1. On the other hand, subjects who have had a primary anti-D response to Rh-positive red cells frequently give a good secondary response to small doses of red cells despite the presence of anti-D in their plasma. The difference in action between the passively-administered and the actively-produced anti-D might lie in the fact that the injected IgG anti-D is derived from a pool of donors and therefore contains a number of IgG antigens which are foreign to the recipient, compared with the autologous nature of the anti-D present after a primary response.