Pathogenesis of ABO hemolytic disease

Abstract

1.1. Observations on 51 families in which ABO hemolytic disease occurred are reviewed. In all but one of the families, the mothers were found to be Group O in conformity with previous reports. This is attributed to the ability of Group O mothers to form antibodies of specificity anti-C as well as anti-A and anti-B.2.2. Affected babies were all either Group A or Group B. Of the Group A babies all but one appeared to be of subgroup A1. The low incidence of subgroup A2 babies is explained by the poor avidity of such red cells for isoagglutinins so that babies of this subgroup are less severely affected by maternal alpha isoantibodies.3.3. Once severe ABO hemolytic disease occurs in a family, then, with rare exceptions, all future babies will be affected unless they belong to Group O.4.4. The incidence of secretors and nonsecretors among the Group O mothers in this series of families was the same as in the general population.5.5. The incidence of nonsecretors among the affected babies, their siblings, and their fathers was lower than in the general population.6.6. When the affected baby is Group A, the titer of the maternal serum for A cells tends to be higher than for B cells and, when the baby is Group B, the reverse is often true. This suggests that in many cases the baby's red cells or body fluids provide the antigenic stimulus accounting for the high titer of the maternal serums. In the remainder of the cases, the alpha and beta antibodies were of equal titers, suggesting predominance of antibody of specificity anti-C and presumably of heteroimmune origin.7.7. It is pointed out that the attempt to distinguish between so-called natural and immune isoantibodies is based on a misconception. All alpha and beta antibodies appear to be of immune origin but, depending on the nature of the antigenic stimulus, the antibodies may be heteroimmune or isoimmune.8.8. Two main patterns of ABO hemolytic disease appear to exist. In one, the maternal isoantibodies are chiefly of heteroimmune origin (so-called “natural” antibodies) and the first-born incompatible baby is generally affected though the manifestations tend to be mild (icterus praecox). In the second form, one or more normal babies of an incompatible blood group may first be born; these babies are secretors and sensitize the mother so that subsequently born babies of incompatible blood group develop typical erythroblastosis. In many of these cases, however, in contrast to Rh hemolytic disease, the first-born incompatible secretor baby may be severely affected.9.9. In general, in cases of ABO hemolytic disease the titer of the maternal alpha and beta isoantibodies is markedly elevated. There appears to be a correlation between antibody titer and severity of the disease, though, as in Rh hemolytic disease, the correlation is not absolute.10.10. The importance of recognizing ABO hemolytic disease is for the intelligent treatment of affected babies and for prognosticating the outcome of future pregnancies.