Analysis of the repertoire of anti‐NP antibodies in C57BL/6 mice by cell fusion. I. Characterization of antibody families in the primary and hyperimmune response

Abstract Spleen cells from C57BL/6 mice sensitized to the hapten (4‐hydroxy‐3‐nitrophenyl)acetyl (NP) were hybridized with myeloma cells, and a variety of hybrid cell lines was isolated which secreted homogeneous anti‐NP antibodies. The antibodies were purified by affinity chromatography and their chain composition, affinity and fine specificity were determined. All antibodies recovered from the primary immune response carried λ light and μ or γ 1 heavy chains. Their variable portions were nonidentical but similar in terms of hapten‐binding specificity with a higher affinity for the cross‐reacting haptens (4‐hydroxy‐3,5‐dinitro‐phenyl)acetyl (NNP) and (4‐hydroxy‐5‐iodo‐3‐nitro‐phenyl)acetyl (NIP) than for the homologous hapten NP. This heteroclitic property as well as the presence of λ, μ and γ 1 chains are characteristic for primary anti‐NP sera of C57BL/6 mice. In contrast, four families of anti‐NP antibodies, each with a characteristic fine specificity pattern, were found among the hybrid cell antibodies derived from the hyperimmune anti‐NP response. The antibodies of one of these families were related to the antibodies recovered from the primary immune response in that they were heteroclitic and carried λ light chains. All members of the other groups expressed k chains and were nonheteroclitic. The finding of well‐defined antibody families in this system and the isolation of their members enable us to approach the problem of V gene expression and diversification in a new way.