Serum Expression of a VK Structure, VK-11, Associated with Inulin Antibodies Controlled by Gene(s) Linked to the Mouse IgCH Complex

Abstract Inulin, β(2 → 1) linked fructofuranan, antibodies (INU-Ab), and a cross-specific idiotype, VK-11, present on the κ-chain of BALB/c inulin-binding myeloma proteins (INUBMP) are detected in mouse serum by solid phase radioimmunoassay systems. BALB/c normal serum contained 5 to 6 μg of VK-11 and INU-Ab/ml, whereas serum from bacterial levan-immunized BALB/c contained 28 to 30 μg of VK-11 and INU-Ab/ml. In contrast, serum from normal and immunized C57BL/6N contained less than 0.25 and 1.0 μg of VK-11 and INU-Ab/ml, respectively. Although not detected in serum by radioimmunoassay technique, INU-Ab was absorbed from large volumes of ascites induced in C57BL/6N by the Tung-Nisonoff method that contained the VK-11 idiotype. INU-Ab and VK-11 levels comparable to BALB/c were found in the Ig congenic strain BC-8 carrying the BALB/c allotype and low-intermediate levels were found in the Ig congenic strain CB-20 (C57BL/6N allotype). INU-ab and VK-11 serum levels comparable to BALB/c were observed in the Bailey RI strains C×BG and C×BJ (BALB/c allotype) whereas the RI strains C×BD (E, H, I and K) with the C57BL/6N IgCH had INU-Ab and VK-11 serum levels comparable to C57BL/6N. Since the BC-8 with the C57BL/6N CK-VK complex must have the VK-11 gene, the BALB/c-C57BL/6N VK-11 strain difference cannot be due to a polymorphism in a VK-11 structural gene. Other genes linked to IgCH appear to control VK-11 and INU-Ab serum expression. Possibly, allelic polymorphism in the VH-5 homolog influences the affinity of the VH-5-VK-11 determined binding site for β(2 → 1) fructofuran and hence the maturation of INU-Ab B cell clones. Alternatively, INU-Ab expression may be regulated by non-Ig structural genes linked to the mouse IgCH complex locus.