Instability of immunoglobulin genes in S107 cell line

Somatic mutation occurs frequently in rearranged and expressed immunoglobulin variable region genes in vivo. In contrast, V region hypermutation seldom occurs in antibody-forming cells in culture. The S107 mouse myeloma cell line is one of the few cell lines that has been observed to generate V region mutations frequently and spontaneously in vitro. Detailed examination reveals that both the S107 tumor and the cell line derived from it contain and express a duplicated heavy-chain gene. In culture, only one of the two heavy-chain genes undergoes both V and C region mutation, and variants with complex phenotypes and genotypes arise as a result of mutation and segregation of these duplicated genes.