Immunogenic properties of two types of sea-squirt antigens

Two antisera were prepared in rabbits against substantially purified preparations of sea-squirt antigens, Gi-rep and Ei-M, which were apparently discriminated from each other in antigenic behavior in radioimmunoassay experiments. Radioimmunometric analysis of the interaction between the two anti-sea-squirt sera and the two antigens revealed that Gi-rep induced in rabbit only one type of antibody (type A) which reacted with Gi-rep and Ei-M in common, while Ei-M induced not only type A antibody having the common reactivity but also another antibody (type B) which was strictly specific to Ei-M. This observation supported the preceding suggestion that Gi-rep and Ei-M carried a common antigenic determinant (type alpha) but that Ei-M had an additional determinant (type beta) specific to Ei-M. In this connection, in view of the similarity of type A antibody in specificity to the blocking antibody induced in asthmatic patients with sea-squirt allergy on hyposensitization therapy with these antigen preparations, it was suggested that the presumed allergenic substance in sea-squirt also carries the type alpha determinant.