Immunogenicity and antigenicity of immunoglobulins. XII. Intact light chain and heavy chain isotype-restricted Vk-associated epitopes.

Immunization with intact IgG has allowed the isolation of four hybridomas producing antibodies recognizing epitopes expressed within subpopulations of human kappa light chains unrelated to known polymorphisms (Km) and previously defined V-region subgroups. The V-region-associated epitopes recognized are conformation-dependent, being expressed on intact light chain but not on isolated VK or CK fragments. The frequency of expression within paraprotein panels of different heavy chain isotypes varied between individual antibodies. An epitope recognized by B2A6, expressed by greater than 85% IgGK paraproteins, was not represented in 16 IgM paraproteins tested, suggesting that association of VK with mu chains does not result in display of the epitope recognized, or alternatively, that selective association between VK and CH gene products occurs. These data contrast with the reactivity of other McAb for CK epitopes which were reactive with isolated CK fragments, and for all kappa-bearing paraproteins, regardless of heavy chain isotypes.