Iso-immunization by rare Rh-antigens as a cause of haemolytic disease of the newborn and transfusion reactions.

It is well known that Rh antibodies develop in persons who are nearly always Rh-negative, either as a result of immunization during pregnancy, or as a result of repeated transfusions when Rh-positive cells are given to Rh-negative recipients. During the last two and a half years we have had an opportunity to study 885 families in which the mothers were immunized by pregnancy. Nearly all these cases were caused by immunization to the D (Rh.) antigen; in some instances, however, antibodies against the C (rh') or E (rh") antigens were developed as well. Of the 13 blood transfusion reactions due to Rh antagonism, all but two were similarly caused by the most important of the Rh antigens, the D or Rho antigen, which was lacking in the recipient. In the literature only a few cases are reported, in which Rh antigens other than D (Rh.)-that is to say the C, E, c, d, or e antigens-have been found to be the only cause of Rh immunization. In this paper we propose to give details of the few exceptional cases due to immunization to these rarer antigens, and to mention at the same time the possibility of producing antibodies against them by artificial immunization.