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Three custom synthesized myelin basic protein (MBP) peptides, bovine peptide 79-88, human peptide 80-89, and human peptide 82-91, were used to produce four murine monoclonal antibodies (MAb) that were selected on the basis of reaction in a solid phase radioimmunoassay (SRIA) with human MBP. The MAb were compared with respect to antigen specificity against intact MBP and 10 overlapping MBP peptides. One MAb recognized an epitope near the amino-terminus of bovine MBP peptide 79-88. A second MAb was directed towards an epitope that is more reactive in human MBP peptide 45-89 than in intact MBP, but is not recognized in any of the small MBP peptides examined. The third MAb detected an epitope near the middle of human MBP peptide 80-89, whereas the fourth MAb reacted with the carboxyl-terminal portion of human MBP peptide 82-91. Epitopes recognized in SRIA were sometimes not detected by the same MAb in a fluid phase double antibody radioimmunoassay. These results demonstrate the multiplicity of potential epitopes in a dodecapeptide of MBP and do not support the concept of a single, dominant epitope in the region of MBP peptide 80-89.

OKT3 and BABR1 [anti-(breast tumour) antibody] were conjugated using N-succinimidyl-3-(2-pyridy]dithio)propionate (SPDP). The procedure employed mild reducing conditions for SPDP-BABR1 and short conjugation incubations at 37 degrees C. The bifunctional immunoconjugates thus produced were isolated by HPLC gel filtration on a preparative TSK 3000 SW column. Both intact IgG and F(ab')2 fragments have been conjugated. The ratio of SPDP to IgG for the optimal yield of dimeric OKT3-BABR1 heteroconjugates was determined to be 2 for OKT3 and 1-2 for BABR1. The OKT3-BABR1 dimers were shown to be bifunctional heteroconjugates by polyacrylamide gel electrophoresis, isoelectric focusing, radial immunodiffusion, and flow cytometry. The binding specificities of the bifunctional heteroconjugates were identical to the specificities of both parent antibodies.