Characterization of a lung cancer-associated human monoclonal antibody HB4C5.

A human monoclonal antibody HB4C5, which is known to be associated with lung cancers, was characterized. Two kinds of light chains with 30-kD and 32-kD molecular mass were found to comprise the molecule of this IgM antibody. Various combinations of the two light chains could be contained in this IgM antibody molecule, which might have resulted in the heterogeneity of this antibody with different reactivities. The presence of the 30-kD light chain was indispensable for the antibody activity of cancer recognition. Monomeric 180-kD units of the antibody, having 32-kD light chains exclusively, which showed marginal activity of cancer recognition, could be removed by immunosorbent column chromatography with histone H2B-Sepharose 4B. F(ab')2 of the HB4C5 antibody containing the active 30-kD component as the dominant light-chain constituent could be purified by hydroxyapatite chromatography by HPLC, facilitating clinical applications of this lung cancer-associated monoclonal antibody of human origin.