Cross-reactive idiotypic determinant

Feizi et al. (1977) have described a heavy-chain variable region marker (VnMar) that was detected using an antiserum raised against human IgM cold agglutinins. Evidence was presented that the relevant determinant was associable with cross-reactive idiotypes characteristic of the cold agglutinins. It was of particular interest that this antigen is found in both normal pooled IgG and some unselected myeloma paraproteins. 

For three other myeloma proteins having anti-(l — 6)-a-D-glucopyranan specificity (W 3129, W 3434, and QUPC 52), the authors found a somewhat different pattern of cross-reactivity.63 The reaction of W 3129 with its anti-idiotypic antibody was not totally inhibitable by even high concentrations of W 3434 protein, and not at all by protein QUPC 52. Thus, proteins W 3129 and W 3434 share some determinants, but are clearly different from each other and from QUPC 52. 

It would be of extreme interest to determine whether any interspecies idiotypic cross-reactions could be observed. Could there be, for example, a cross-reaction between idiotypic determinants on an antibody of given specificity (say, antidinitrophenol) produced in a second species. To the authors knowledge, no reports of such cross-reactivity have yet appeared. However, the basic unity observed in the construction of the antibody-combining-site structure, at least among mammalian species, would suggest that such interspecies cross-reactivity is a very real theoretical possibility. 

---