Mutations in immunoglobulin-producing mouse myeloma cells

Three mouse myeloma cell lines were cloned in soft agar and screened by an antiserum overlay method for variants defective in secretion of the myeloma protein. Variants that had lost the capacity to synthesize heavy chains arose spontaneously at a high rate of about 10(-3) per cell per generation. Such variants lost the capacity to produce light chains at a similarly high rate. After cells were treated with the acridine half mustard ICR-191, variants occurred with an even higher incidence, and some of these synthesized heavy chains differing from that of the parent.