Immunochemical Classification of Nonisolated Light Chains of Immunoglobulins

Antigenic sites of the light chain are often masked in the intact immunoglobulin (Ig) molecule; and because many of our anti-light chain antisera have stronger reactivity with the free light chain than with the intact Ig molecule, a microtechnique for reduction and alkylation of homogeneous immunoglobulins which does not require isolation of the light chain before immunochemical typing was used in preparation of type K myeloma proteins and M macroglobulins for immunochemical analyses without group-specific antisera. Antisera specific for κI, κII, κIII, and κIV light chains were used in immunodiffusion analyses of the reduced and alkylated Ig; antigenic identity between the treated Ig and homologous isolated light chain was readily demonstrable. The classification of the light chains of proteins of known antibody activity, e.g., cold agglutinins, as well as the study of proteins available in small quantity, was facilitated by the use of the microtechnique for reduction and alkylation.