[Switch in the synthesis of IgM--IgG antibodies. I. Ratio of allelic variants of light rat immunoglobulin chains in antilactoside antibodies of different classes].

Ratio of allelic variants was studied of the rat immunoglobulin light chains in IgM and IgG fractions of anti-lactoside antibodies isolated from the sera of immune heterozygous rats (WAGXMSU)F1 and (AugustXMSU)F1. For MSU rat strain, RL1 allelic variant of light chains is typical whereas WAG and August strains possess the RL2 variant. Anti-lactoside antibodies isolated from sera of F1 rats were separated into high affinity and low affinity fractions. Thereafter each fraction was divided into IgG and IgM classes and each preparation was tested for the content of the molecules of the antibodies with light chains of RL1 and RL2 type. It has been shown that the ratio of allelic variants coincides in IgM and IgG antibody fractions. It follows from this fact that the IgG switch of antibody synthesis may process in the same cell during development of the given population of antibody-producing cells.