Guinea pig immunoglobulin light chain isotypes. II. The preferential expression of lambda chain-bearing anti-phenyltrimethylammonium antibodies is associated with restricted variable region expression, but not with any alteration in the proportion of lambda chain constant region isotypes, relative to normal immunoglobulins.

The inbred strain 13 guinea pig expresses at least three isotypes of immunoglobulin (Ig) lambda chain. The proportion of these isotypes in normal Ig can be estimated by isolating a constant (C) region cyanogen bromide peptide from lambda chains and quantitatively analyzing its component tryptic peptides. Anti-phenyltrimethylammonium antibody, when analyzed in this way, was found to contain the same proportion of each lambda chain C region isotype as did normal Ig. The specific antibody light (L) chain pools were found to contain predominantly lambda chains, although these are the minority type in guinea pig normal Ig L chain pools. Moreover, amino-terminal, 5-pyrrolidone-2-carboxylic acid-containing peptides isolated from antibody lambda chains show no demonstrable sequence heterogeneity, while their homologs isolated from normal lambda chains are markedly heterogeneous. That a restriction in heterogeneity of variable region framework residue positions is not associated with any alteration in the proportion of C region isotypes in these antibody lambda chains, implies that translocation of all guinea pig lambda chain variable region genes to the isotypic C region genes occurs in a random way.