A MURINE MONOCLONAL MULTIREACTIVE IMMUNOGLOBULIN-KAPPA LIGHT-CHAIN

N12.12 is a monoclonal immunoglobulin (Ig) kappa light chain (KLC) sec reted 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 g el electrophoresis (SDS-PAGE) of the S-35-methionin biosynthetically l abelled proteins secreted by the cells. It was shown that N 1 2.12 KLC reacted with mouse actin, trinitrophenylated bovine serum albumin (TN P25-BSA) and weakly with bovine myoglobin. The binding of the N 1 2.12 'monoclonal antibody' to mouse actin or to TNP25-BSA was inhibited sp ecifically by both antigens with a dissociation constant (K(D)) for bi nding 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 bin ding characteristics usually attributed to natural multireactive antib odies.