Quantitative studies on antigenic recognition. IV. Specific inhibition of the recognition process by alloantisera

In mixed spleen cell cultures in which one partner was of parental strain origin and capable of recognizing transplantation antigens of the other partner, which was of a corresponding F1 hybrid origin, recognition of antigens was revealed by the elaboration of a product of antigenic recognition (PAR) in culture super‐natants. Recognition of antigens could be blocked by neutralizing them with alloantisera obtained from animals that had rejected allogeneic skin grafts. Inhibition was highly specific in that serum treatment of F1 hybrid cells blocked only one or the other of the two antigenic specificities present. In none of the situations tested did these alloantisera interfere with recognition when used to treat parental strain cells. It could also be shown that putative neutralization of antigens on parental strain aggressor cells did not affect their ability to recognize. As revealed by inhibitory titers, alloantisera were of different strengths. Activity could be demonstrated in sera of highly incompatible strain combinations of rats and mice, but also in those of Syrian hamsters. Furthermore, alloantibody activities were shown to be present in sera of mice following rejection of non‐H‐2 different skin grafts and even in an antiserum resulting from the weak H‐Y determined incompatibility.