Specific and cross-reacting antibodies in ABO heterospecific twin pregnancy

A "study in depth" is reported concerning the case of hemolytic disease of agroup B infant born to a group O mother, whose group A twin was apparentlyunaffected. It was shown that the hemolytic disease of the affected infant wasdue to a specific anti-B antibody. The study included parallel examinations ofthe antibodies in the sera of the three individuals.

The specificity of the B-anti-B reaction was demonstrated in vitro and in vivo.The powerful anti-B antibody of the mother had no effect on the group A twin,in whose serum anti-B was present in large amounts.

In vitro, studied by the usual technics of cross absorption the maternaland the fetal anti-A and anti-B serum antibodies behaved as if strictly specific.By applying successive absorption, elution and neutralization techniques, however, it was possible to demonstrate additional cross-reacting antibodies in thematernal serum which could be separated from one another and from the specificanti-A and anti-B antibodies. From the erythrocytes of the normal group Atwin such cross-reacting antibody could be eluted.

The cross-reacting anti-B antibody, isolated in pure form in eluates, could beshown to be loosely attached to group A erythrocytes without producing visibleagglutination reactions while after elution from A cells it did visibly agglutinategroup B cells. It could be eluted from A cells, absorbed by fresh A cells and reeluted while retaining its anti-B effect. It was neutralized by group B saliva only.A separate anti-A antibody with similar properties was eluted from B cells andspecifically neutralized by group A saliva.

A partial affinity of these antibodies for heterologous erythrocytes but not forspecific soluble substances was thus demonstrated. These findings support neitherthe linkage hypothesis of cross reactions between anti-A and anti-B nor theC-anti-C hypothesis of hemolytic disease. They are in keeping with the view thatgroup O sera contain variable complexes of anti-A and anti-B antibodies, composed of multiple fractions with different partial specificities. It is suggested thatthe occurrence or non-occurrence of cross-reacting antibodies found in sera ofgroup O mothers whose infants develop hemolytic disease is best explained onthis basis. It is further stressed that the demonstration of an antibody in motheror child in ABO hemolytic disease does not necessarily indicate its pathologicsignificance.

Submitted on January 11, 1957 Accepted on April 19, 1957