The immune response to ferredoxin: characterization of a major idiotype in serum using monoclonal antibody derived by cell fusion.

Ferredoxin (Fd) is a low mol. wt protein (6000 d) isolated from Clostridium pasteurianum. This antigen possess two non-cross-reactive antigenic determinants and engenders a restricted antibody response in selected strains of mice. Immunochemical studies of Fd have shown that antibody responses are confined to two sequences of between five and seven amino acids in extent located at the NH2-and COOH-termini of the molecule. Serum antibodies from responder strains of mice bind these epitopes in proportions which are regulated by genes mapping in the Ir-region of the H-2 complex. A hybrid cell line secreting monoclonal Fd-binding antibody has been isolated from an immune mouse through fusion with the SP2/0 myeloma cell line. The resulting antibody binds to a single determinant located at the nH2-terminal of the molecule. An anti-idiotype antibody to this monoclonal antibody was raised in rabbits. After appropriate absorptions, its specificity for the paratopic regions of the hybridoma antibody was established by demonstrating its displacement from reaction with the idiotype by Fd. Analysis of the distribution of the hybridoma idiotype in serum antibodies from congenic mouse strains indicates that it is a major idiotype expressed in different inbred strains sharing identity at the Igh-1 locus.