354 Anti - Phosphocholine Hybridoma Antibodies

Three major groups of antibodies have been identified during the analysis of the clonal response to phosphoeholine (PC). t The predominant one shows multiple molecular features of the PC-binding myeloma protein (PC-BMP) TEPC 15 (1-3), and two others possess idiotypes (Id) and L-chain characteristics of two other PCBMP, M511 (2, 4) and M603 (5). All three Id groups are conserved in inbred mice (1, 2, 4-6). Serological studies indicate that antibodies sharing Id with M511 or M603 are both heterogeneous, i.e., each is a distinct family of antibodies whose members appear to be closely related to each other (4, 5). In contrast, normally expressed T15 Id + antibodies appear to be virtually homogeneous (6), although in one Igh haplotype we have recently identified at least three distinct antibodies that bear T 15 Id (7). To evaluate the clonal response at both the protein and chromosomal levels, we have generated and studied a large series of hybridoma cell lines from different strains, all produced by fusion with the nonsecreting cell line SP2/0-Agl4. The present investigation describes the relationships among these hybridomas, with particular emphasis on family membership, L-chain features, and antigen-binding characteristics. We find that hybridoma anti-PC antibodies are divided into three families, each of which resembles one of the three major groups of antibodies seen after immunization. The antigen-binding properties of the hybridoma anti-PC antibodies in a family are similar to each other and to the prototype PC-BMP, with one striking exception. Moreover, we have found that there is not necessarily a direct correlation between binding specificity and idiotypy or chain structure. Thus, we have verified our previous findings on the composition and conservation of the anti-PC repertoire in mice but suggest in addition that structural variation (including idiotypy) may not always translate into demonstrable changes in antigen-binding diversity.