title: Idiotypic cross-reactivity of low-affinity anti-fluorescyl monoclonal antibodies.
abstract: Previous studies concerning structure-function relationships of anti-fluorescyl hybridoma proteins utilized primarily high-affinity proteins (Ka greater than 5.0 X 10(7) M-1) possessing distinct idiotypes. Low-affinity anti-fluorescyl monoclonal antibodies, predominantly IgGl or IgG2a possessing kappa light chains were analyzed. Two fusions produced 18 monoclonals, 13 binding fluorescein with a low affinity (less than or equal to 3.0 X 10(6) M-1) and five possessing high affinities (greater than or equal to 5.3 X 10(8) M-1). Solid-phase idiotype assays, utilizing rabbit anti-idiotype reagents against two low-affinity proteins (3-13 and 3-17), showed that all the low-affinity clones (except 2-9 and 2-21) were capable of inhibiting (40-100%) these two idiotype-anti-idiotype interactions while no high-affinity proteins inhibited them. The interactions with 3-13 and 3-17 were inhibited 100 and 88%, respectively, by free fluorescein. When these idiotype-anti-idiotype interactions were inhibited with increasing concns of heterologous hybridoma proteins, three clones inhibited both interactions as effectively as the homologous proteins at all concns tested and inhibition reached 100%. These three clones appeared to possess all the idiotopes that the anti-3-13 and anti-3-17 reagents detected on 3-13 and 3-17. Screening of eight high-affinity anti-fluorescyl proteins previously produced [Kranz and Voss, Molec. Immun. 18, 889-898 (1981a)] identified a single clone [20-4-4 (Ka = 5.0 X 10(7) M-1)] significantly inhibiting the 3-13 and 3-17 interactions (71.0 and 63.6%, respectively). In addition, recombination experiments utilizing H- and L-chains derived from three low-affinity and three high-affinity antibodies resulted in reformation of active sites in all six heterologous combinations when both chains were derived from low-affinity antibodies, and in only one of six combinations when both chains were derived from high-affinity molecules. Thus, the apparent lack of private idiotopes on clones 3-13 and 3-17 and the presence of these idiotopes (or cross-reactive ones) on 11 of 13 low-affinity antibodies and on one of 13 high-affinity antibodies may indicate that clones 3-13 and 3-17 are encoded by germline genes. The H- and L-chain recombination experiments indicated that the idiotype and affinity of parental molecules may be involved in H- and L-chain association.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000915:Antibody Affinity; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D016650:Fluorescein-5-isothiocyanate; D005452:Fluoresceins / Q000276:immunology*; D007143:Immunoglobulin Heavy Chains / Q000276:immunology; D007130:Immunoglobulin Idiotypes / Q000276:immunology; D007147:Immunoglobulin Light Chains / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D013861:Thiocyanates / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D005452:Fluoresceins; D007143:Immunoglobulin Heavy Chains; D007130:Immunoglobulin Idiotypes; D007147:Immunoglobulin Light Chains; D013861:Thiocyanates; D016650:Fluorescein-5-isothiocyanate