Repertoire of murine λ-positive variable domains: polyclonal induction of λ isotypes and their associated pattern of antibody specificities

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Abstract
The diversity of λ variable (Vλ) domains is extremely restricted when compared to those of VH and Vλ. In addition, each Vλ domain is determined by the Cλ domain, For these reasons, the λ system is an excellent model for the study of the associated VH region repertoire. The study of Vλ domain diversity has been limited by the small contribution (approximately 5%) of λ‐bearing proteins to the total Ig pool. We now show that treatment of BALB/c mice with rabbit anti‐λ1 antibodies coupled to lipopolysaccharide induces a production of polyclonal λ1 light chain‐bearing Ig whereas, conversely, treatment with rabbit anti‐λ2 antibodies induces a production of polyclonal λ2 + λ3 light chain‐bearing Ig. The antigenic specificities of these two distinct λ populations were then studied using B1355 dextran, (4‐hydroxy‐3‐nitrophenyl)acetyl (NP) and 2,4‐dinitrophenyl (DNP) as antigens. The anti‐α(1‐3)dextran antibody specificity was found to be mediated exclusively by antibodies bearing the λ1 isotype whereas the anti‐NP and anti‐DNP antibody specificities are mediated by both the λ1 and λ2 + λ3 isotypes. In addition, various mouse strains with the VHa or VHb allotypic haplotype and the r or r phenotype were treated with rabbit anti‐λ1 antibodies. The λ1 anti‐NP and anti‐DNP antibody specificities were similar in all strains whereas the λ1 anti‐α(1‐3)dextran specificity was linked to the presence of the VHa allotypic haplotype. The mouse strains with the r or r phenotype did not differ in terms of their patterns of λ1 antibody specificities.