Variants of mouse myeloma cells that produce short immunoglobulin heavy chains

After mutagenesis of cultured mouse myeloma cells with ICR 191 or mephalan, variant clones were isolated that synthesized immunoglobulin heavy chains shorter than those produced by the parent. These variants fell into 2 phenotypes, based on the size, serology, and pattern of assembly of the heavy chain. Variant chains of both types no longer reacted with antisera directed either against the Fc (C terminal half of the heavy chains) or subclass specific IgG(2b) determinants. Comparative ion exchange chromatography of tryptic chymotryptic peptides confirmed that the variant heavy chains differed structurally from those of the parent and from each other. A conversion from one phenotype to the other was observed. (18 references.)