Passive Antibodies Other Than Anti-D Through RhIG?

 RhIG and its many brand names (Rhophylac, WinRho, RhoGAM, etc) is derived from human blood plasma containing the anti-D antibody. Plasma is harvested from healthy Rh negative donors who are intentionally alloimmunized with with the RhD antigen. Those with an active immune response will create Anti-D in 1 to 2 weeks time. The donor can then provide plasma to RhIG manufacturers to create the RhIG Anti-D drug. The donors may even need to be re-stimulated with Rh positive cells to produce more antibody. 

These alloimmunization events give rise to the chance for OTHER red cell antibodies to be formed as well. If given enough vials of RhIG it is absolutely possible to see these antibodies reflected in the antibody screen of an RhIG recipient. We see a positive screen for the Anti-D (as a passive anti-D) so why not for a Kell? C? Jka? It's possible and it has happened. 

Take for instance a patient that needed a six vial injection of RhIG due to a Fetomaternal Hemorrhage. The RhIG vials were quantified via Kleihauer Bekte stain. The next antibody screen performed on this patient showed not only a passive Anti-D but ALSO an Anti-C. It is unlikely, given how quickly the reactivity manifested, that this was due to true alloimmunization. The RhIG package insert was consulted, and it does indeed say passive transfer of other non Anti-D antibodies is also possible, especially anti-C. Package inserts of many other RhIG brands have information like this with some claiming the possibility of passive Kell, passive Kidd, passive Duffy, etc. The patient had Passive Anti-C placed in there file, and a note to follow up 6 months down the road for an additional antibody screen. 

This presents a challenge for those in need of transfusion support, because even though the patient may not be truly creating the antibody, they likely should receive antigen negative blood until the RhIG has been removed from circulation. The more vials given per event, the more likely we are to come across this scenario. A pre-event antibody screen could be helpful in determining passive vs alloantibody.