Idiotypic determinants cross-reactions

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. 

Amyloid proteins related to immunoglobulin possess individually specific (idiotypic) antigenic determinants i.e., such amyloid proteins from different individuals possess unique primary structures. Idiotypic determinants characteristic of a given amyloid protein can sometimes be detected in the serum of the same individual. In addition, however, amyloid proteins of a given type (it or X) frequently have shared antigenic determinants (120,124,126). Antiserum directed to an amyloid protein will, in general, cross-react weakly with normal L chains of the same type. It seems likely that these cross-reactions are attributable, in the case of the smaller amyloid proteins, to shared V region sequences. 

Antisera were prepared in rabbits against the isolated monoclonal IgG and IgM and rendered specific for idiotypic determinants by appropriate absorptions (76). No cross-reactions were observed in tests with over 30 sera from other patients with multiple myeloma. Antiidiotypic antiserum to Til IgG gave a line of identity in its reaction with Til IgG and IgM. The antiidiotypic serum to Til IgM formed two lines in reacting with Til IgM, one of which showed identity with Til IgG. 

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. 

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