A murine monoclonal multireactive immunoglobulin kappa light chain.

N12.12 is a monoclonal immunoglobulin (Ig) kappa light chain (KLC) secreted by a B-cell hybridoma derived from spleen cells of a normal SJA mouse. No heavy chain was detected in the culture supernatant of this hybridoma using an enzyme immunoassay (EIA) and after polyacrylamide gel electrophoresis (SDS-PAGE) of the 35S-methionin biosynthetically labelled proteins secreted by the cells. It was shown that N12.12 KLC reacted with mouse actin, trinitrophenylated bovine serum albumin (TNP25-BSA) and weakly with bovine myoglobin. The binding of the N12.12 'monoclonal antibody' to mouse actin or to TNP25-BSA was inhibited specifically by both antigens with a dissociation constant (KD) for binding to mouse actin of 10(-7) M. The results indicate that a free KLC can bind both to mouse and to non-mouse molecules, thus exhibiting binding characteristics usually attributed to natural multireactive antibodies.