Characterization of the NP a idiotype through the analysis of monoclonal BALB/c anti‐(4‐hydroxy‐3‐nitrophenyl)acetyl (NP) antibodies

Spleen cells from BALB/c mice were fused with the nonsecreting myeloma line X63.Ag8.6.5.3 seven days after immunization with NP‐CG (4‐hydroxy‐3‐nitrophenyl) acetyl‐chicken γ‐globulin. The hybrid cell lines obtained were analyzed for heavy and light chain distribution, fine specificity, and idiotype. The majority of monoclonal antibodies possessed either γ 1 or μ chains. The distribution of L chains among these antibodies was approximately half λ and half ϰ. Thirteen monoclonal antibodies were grown as ascites tumors in mice. Examination of their fine specificity patterns showed that all of the λ antibodies are heteroclitic and have similar fine specificity patterns. Five of the seven ϰ antibodies are also heteroclitic, but their fine specificity patterns are more heterogeneous than those of the λ antibodies. Polyspecific anti‐idiotypic sera directed against pooled primary serum antibody (R ā‐NP a ) or against individual monoclonals were used for idiotypic characterization of the monoclonal antibodies. The R ā‐NP a bound all of the λ antibodies but none of the ϰ antibodies suggesting that the ϰ antibodies may be much more heterogeneous and were therefor not recognized in the presence of the more homogeneous λ antibodies. Further idiotypic analysis demonstrated that the λ antibodies, although no two are identical, are a very homogeneous group of antibodies which cross‐react with one another but not with the ϰ antibodies. Some, but not all, of the ϰ antibodies cross‐react with each other although none are cross‐reactive with the λ antibodies. Because the λ‐associated idiotype is recognized by the R ā‐NP a and its characteristics are similar to that of the C57BL/6 major idiotype (NP b ), it is referred to as NP a . There may be a second major idiotype associated with at least some of the ϰ antibodies.