STRUCTURAL-ANALYSIS OF A PHOSPHORYLCHOLINE-BINDING ANTIBODY WHICH EXHIBITS A UNIQUE CARRIER SPECIFICITY FOR TRICHINELLA-SPIRALIS

A phosphorylcholine (PC)-binding IgG (Mab2) antibody produced by a hyb ridoma derived from a BALB/c mouse which had been immunized against Tr ichinella spiralis was found to bind to the immunizing antigen (TSC) b ut not to other PC-associated antigens such as pneumococcal antigen (P NC) and PC-conjugated ovalbumin (PC-OVA). Sequence analysis of the pro tein revealed the presence of a heavy chain (V-H) which was very simil ar (differing in only four amino acids) to that of the M511 myeloma pr otein, and a light chain (V-L) which was completely identical to that of the M167 myeloma protein. Several M511/M167(+) proteins, including the prototypic M511 protein and PC-binding proteins of other families (TEPC 15 and W3207), were examined in their binding to the various PC- associated antigens. These were found to be largely indiscriminate alt hough subtle differences were observed for some antigens with some of the antibodies. A comparison of the VH sequences of Mab2 and these pro teins revealed that of the differences seen, the single most important substitution in Mab2 which could contribute to the unique specificity of the molecule is the glycine residue at 49H. None of the other prot eins, including other PCV-binding proteins published to-date, which ut ilize the same VH segment (99 in total), has this substitution.