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

Abstract

The diversity of λ variable (V_λ) domains is extremely restricted when compared to those of V_H and V_λ. In addition, each V_λ domain is determined by the C_λ domain, For these reasons, the λ system is an excellent model for the study of the associated V_H region repertoire. The study of V_λ 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 V_H^a or V_H^b 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 V_H^a allotypic haplotype. The mouse strains with the r or r phenotype did not differ in terms of their patterns of λ1 antibody specificities.