BASILEA rabbits express two types of immunoglobulin light chains: lambda and kappa-like.

Abstract

In the variant rabbit strain BASILEA, immunoglobulins G were shown to contain two distinct populations of IgG molecules whose light (L) chains belonged to the known A isotype and to a new K-like type. These two L chains differed from each other by electrophoretic, chemical, and antigenic properties. The K-like L chain fraction showed (i) an acid-labile Asp-Pro bond at the end of the joining region and (ii) a tryptic peptide, whose amino acid sequence ofthe NH2-terminal 15 residues was identical to the homologous constant (C) region sequence of b9 K chain with the exception of the residue in position 70, which is asparagine in the K-like chain instead of the characteristic half-cystine residue in all L chains of KB type expressing b4, b5, b6, or b9 allotypes. Serological and chemical studies have demonstrated to date the existence of five polymorphic forms of the domestic rabbit K light (L) chain allotypes designated b4, b5, b6, b9, and b4var (1-6). Extensive chemical differences in the constant (C) regions of b4, b5, b6, and b9 molecules have been reported (7-9) and are thought to reflect the expression of the antigenic determinants of the b allotypes (10). In standard domestic rabbits, A-type L chains are the minor component of the immunoglobulin L chain pool (11). However, this situation is reversed in a variant rabbit strain designated BASILEA, which was developed and maintained by Kelus and Weiss (12). Homozygous BASILEA rabbits are characterized by the lack ofK chains bearing b4, b5, b6, or b9 allotypic markers, which are substituted by L chains of the A type bearing C7 and C21 allotypic specificities (12-14). The primary structure of the constant region ofA L chains derived from an antibody IgG raised in BASILEA rabbits was recently completed and showed extensive homology with A chains of other species (14,15

Kappa-chain allotypes and isotypes in the rabbit: cDNA sequences of clones encoding b9 suggest an evolutionary pathway and possible role of the interdomain disulfide bond in quantitative allotype expression.

“…Recently, a Basilea strain of rabbit has been developed that expresses low amounts of bas K light chains and exhibits compensatory production of X light chains (4). Experiments from four laboratories indicate that bas is an isotypic form of rabbit K (K2) (5)(6)(7)(8)(9)(10). These and earlier observations of latent (unexpected) allotype expression have led to proposals that rabbit K allotypes are in fact isotypes whose expression is regulated in allelic fashion (11)(12)(13)(14).…”

A second rabbit kappa isotype.

“…These light chains are distinct from the b-positive kappa light chains present in the sera of conventional rabbits (14). In this paper we present serological and genetic data demonstrating that anti-bas sera are directed against an allotypic form of a kappa isotype (~2) different from the kappa isotype (~1) that bears allotypic specificities of the b series, and that the loci controlling the expression of ~ 1 and ~2 isotypes are closely linked.…”

“…These antisera reacted with sera from rabbits homozygous or heterozygous with respect to the bas gene and with sera from some b9-positive rabbits from the Basel Institute of Immunology, but not with all other domestic rabbit sera tested, including those that are b9-positive (13,14).…”

“…Alloantisera were raised by immunizing "conventional" rabbits with immunoglobulins (Ig)isolated from the sera of homozygous bas/bas rabbits (13,14). These antisera reacted with sera from rabbits homozygous or heterozygous with respect to the bas gene and with sera from some b9-positive rabbits from the Basel Institute of Immunology, but not with all other domestic rabbit sera tested, including those that are b9-positive (13,14).We have recently obtained chemical and serological evidence that anti-bas sera are directed against antigenic determinants of kappa light chains present in the sera of rabbits homozygous or heterozygous with respect to bas gene. These light chains are distinct from the b-positive kappa light chains present in the sera of conventional rabbits (14).…”

“…The homozygous bas/bas Basilea rabbits compensate for their lack of b allotype-positive kappa chain by producing elevated amounts of lambda-type light chains (11,12). Alloantisera were raised by immunizing "conventional" rabbits with immunoglobulins (Ig)isolated from the sera of homozygous bas/bas rabbits (13,14). These antisera reacted with sera from rabbits homozygous or heterozygous with respect to the bas gene and with sera from some b9-positive rabbits from the Basel Institute of Immunology, but not with all other domestic rabbit sera tested, including those that are b9-positive (13,14).…”