Primary structure of the variable regions of a monoclonal antibody MUSE11 recognizing the tandem repeat domain of a mucin core protein, MUC1.

A monoclonal antibody (MAb) MUSE11 recognizes an epitope in the tandem repeat domain of a mucin core protein, MUC1. We show that the epitope of MAb MUSE11 could be within the continuous amino acid sequence PDTRPAPG. Since there is increasing evidence indicating that this region is highly immunogenic, cDNA cloning of the variable regions of heavy-chain (VH) and of light-chain (VL) of MAb MUSE11 was performed by using RT-PCR to provide a basis for analyzing the structure of the antibody-antigen complex and for producing anti-idiotypic antibodies. The deduced amino acid sequence revealed that the VH and VK of MAb MUSE11 could be assigned to subgroups IIIA and II of mouse immunoglobulin heavy and light chains, respectively. When compared with the V regions of other MAbs in the same subgroup, the complementary determining region 3 (CDR3) in the VH region of MAb MUSE11 consisted of a unique sequence that may be important in defining the specificity of MAb MUSE11.