Serologic distinction between the rabbit kappa L chain allotype b4 and an allele b4

Rabbit kappa light (L) chain allotypes are controlled by the allelic genes b4, b5, b6, b9 and a recently described allele b4v. The product of the b4v gene differs from that of b4 by at least two amino acid substitutions in the constant region. A serologic distinction between the b4 and b4v allotyes has now been detected by a radioimmune assay using one of six anti-b4 sera tested. The distinction was enhanced by fractionation of this antiserum on an immunoadsorbent containing cottontail rabbit IgG. IgG with L chains of the b4v type are deficient in their ability to inhibit binding of b4 IgG to the antibody preparation. L chains isolated from b4 and b4v IgG samples could not be distinguished by this assay indicating that interaction with an H chain is required for expression of the L chain determinants that differentiate b4 from b4v.