Loss of an individual idiotype on chemical modification. A strategy for assigning idiotypic determinants.

Abstract

Two dextran-binding [mouse] myeloma proteins, J558 and Hdex 24, which possess the same individual idiotype (IdI) were diazotized to low levels (1-3.3 groups per subunit) with 1-[14C]-p-aminobenzoate. Both proteins lost the IdI under these conditions with most of the label incorporated on the H chains of each protein. When the diazotization was carried out in the presence of the hapten 1-O-methyl-.alpha.-D-glucopyranoside the loss of idiotypic reactivity could be prevented for J558, but not for Hdex 24. Under these conditions most of the label was incorporated on the L chains of J558, but on the H chains of Hdex 24. For J558, a major determinant of the individual idiotype is within the hypervariable positions of the H chain. For Hdex 24, the determinant being modified is on the H chain but is not involved in hapten binding. These results are consistent with previous work showing that J558 and Hdex 24 differ in amino acid sequence in the D and the J segments of the H chain and offer an alternative and complementary strategy for assigning idiotypic determinants.