ANTIHAPTEN ANTIBODY SPECIFICITY AND L CHAIN TYPE

Two types of light polypeptide chain (κ and λ) are present in guinea pig immunoglobulins. The ratios of K/L molecules in anti-hapten antibodies differ sometimes markedly from that found in normal serum. Anti-DNP antibodies and anti-pipsyl antibodies have, respectively, a higher and a lower than normal K/L ratio. The possibility that the L chain type affects the range of configurations which the antibody-combining site may assume was investigated. Fractional precipitation of anti-DNP antibodies from serum of guinea pigs immunized with DNP₄₄-BSA was performed using limiting amounts of antigen. Antibody fractions were purified from each precipitate, their affinities for ϵ-DNP-L-lysine measured by fluorescence quenching (K₀) and the K/L ratio estimated by precipitation with specific antisera. Increasing concentrations of L molecules were found in fractions with decreasing K₀. In other experiments, fractional precipitation and purification of antibodies which cross-react with DNP was performed in serum of animals immunized with pipsyl-BGG. The K/L ratio in antibodies isolated from these fractions was much higher than in fractions which do not cross-react with DNP. These results show that K molecules are better adapted to react with the DNP hapten than L molecules. The K/L ratio in anti-DNP antibody was shown to increase in the course of immunization, at the same time that the K₀ is increasing. This rise in K₀ is markedly delayed when larger doses of antigen are employed.