UV light-induced immunoglobulin heavy-chain class switch in a human lymphoblastoid cell line

During attempts to select nonsecretory variants from 0.467.3, an Epstein-Barr virus-transformed human lymphoblastoid cell line¹ that secretes small amounts of IgM λ, we exposed the cells to UV light. Cells that survived the irradiation were subcultured and their supernatants were screened for immunoglobulin production by an enzyme-linked immunosorbent assay (ELISA). Although stable nonsecretory variants were not isolated, we report here that an immunoglobulin class switch occurred in the UV-treated cell population. All survivors were found to produce large quantities of IgG λ. Some cell cultures also produced the original IgM λ. The UV-light-induced class switch was regularly reproducible with this target cell line.