Multiple individual and cross-specific indiotypes on 13 levan-binding myeloma proteins of BALB/c mice

13 leven-binding myeloma proteins (LBMP) of BALB/c origin were classified into two groups with different binding specificities; one group of 11 proteins bound beta2 leads to 1 fructosans, a second group of two proteins bound fructosans probably of beta2 leads to 6 linkage. Anti-idiotypic sera prepared to 10 of the proteins in the appropriate strains of mice identified numerous idiotypic determinants. Each protein used for immunization had its own unique individual idiotypic specificities (IdI) and in addition most of the proteins carried two- nine cross-specific or shared idiotypes (IdX) that were found only among LBMP, and not found in 106 non-LBMP. Most of the IdX determinants and only four of the IdI determinants of the beta2 leads to 1 fructosan binding group were located in the antigen-binding site. The multiplicity of antigenic differences in this functionally related group of immunoglobulins reveals an unexpected degree of heterogeneity in V-regions that appears to be unrelated to binding.