Complement fixation by Rh blood group antibodies

Rh blood group antibodies normally do not fix complement. Rh positive intact red blood cells treated with papain do not lyse when incubated with corresponding antibody and complement. This study was done to determine if complement fixation occurs when antibodies were combined with Rh positive red blood cell ghosts untreated or treated with papain. Complement fixation was observed with IgG anti-D, anti-DC and anti-c when papain treated ghosts were used. No complement fixation or a smaller degree of it was observed in the case of untreated Rh positive red blood cell ghosts when incubated with similar anti-Rh antibodies. It is concluded that the papain treatment of Rh positive red blood cell ghosts, possibly by inducing aggregation of antigen sites, allowed complement binding by Rh antibodies.