A novel guinea pig macrophage-specific polymorphic molecule. II. Biochemical analysis of the polymorphism.

We have identified a macrophage-specific molecule, termed gp98, which has a m.w. of 98,000, is encoded by a gene not linked to the guinea pig lymphocyte antigen complex, is highly immunogenic, and displays a serologic polymorphism among several inbred guinea pig strains. The gp98 molecule was biochemically analyzed to identify a basis for the serologically detected polymorphism. The molecule was demonstrated to be a glycoprotein containing N-linked oligosaccharides. The strain 2 serologic variant, gp98-2, migrated with an apparent m.w. approximately 2500 more than did the strain 13 variant gp98-13. This differential migration was observed in a (strain 2 X strain 13) F1 animal, and persisted after neuraminidase and endoglycosidase F treatment, and after reduction. Trypsin and endoproteinase Lys-C digestion localized the biochemical basis of the polymorphism to the peptide portion of the molecule. Biochemical analysis of the gp98 molecules from five different inbred strains indicated that only two biochemical variants correlating with the serologic variants existed among the five strains.