Variants of a mouse myeloma cell line that synthesize immunoglobulin heavy chains having an altered serotype

Cells of the MPC 11 mouse myeloma cell line, which produces an IgG(2b) immunoglobulin, were subjected to mutagenesis with Melphalan or with ICR 191, after which they were cloned in soft agar. Approximately 0.5% of the clones produced altered heavy chains that: (i) were the same size as or larger than the parent; (ii) no longer were recognized by antibody specific for the parent γ2b subclass; (iii) were recognized by antibody specific for the γ2a subclass; (iv) were recognized by antibody against the Fab (NH₂ terminal half) of the parental immunoglobulin, but lacked some of the antigenic determinants of the Fc (COOH terminal half) of the heavy chain; (v) lacked many of the tryptic/chymotryptic peptides found in the parent; (vi) contained tryptic/chymotryptic peptides that were not present in the parent but were present in an unrelated γ2a myeloma heavy chain; and (vii) assembled with light chains by a pathway typical of IgG(2a) myelomas.