title: IgE production in vitro by two rat myeloma tumor lines (IR2 and IR162).
abstract: Two IgE-synthesizing rat myeloma tumor lines (IR2 and IR162) were maintained in growing cultures that were viable for prolonged periods of up to three months in the presence of primary fibroblasts. The production of IgE by explanted tumor cells was studied in short-term and long-term cultures. The IR 162 tumor line retained expression of both IgE heavy (H) and light (L) chain synthesis for up to three months under in vitro conditions, while the IR2 tumor line initially lost H chain expression after approximately one month in culture, followed by subsequent loss of L chain about one month later. Total polysomal RNA extracted from IR2 cells, before and after loss of IgE-expression, was separated by sucrose gradient centrifugation, and gradient fractions were analysed for poly(A)-containing mRNA by a [3H]poly(U)binding assay. The results for the long-term IR2 cultures showed a disappearance of mRNA sedimenting at 18-20 S and 15 S, found to represent H and L chain mRNAs, respectively. Furthermore, no IgE L chain mRNA sequences could be detected in long-term IR2 cultures when analysed by hybridization assays, using as a probe a 3H-labelled DNA complementary to IgE L chain mRNA, L chain mRNA sequences were also absent from the nuclear RNA in long-term IR2 cultures. The loss of IgE synthesis in long-term cultures of IR2 cells therefore appears to be correlated with a concomitant loss of IgE mRNA sequences indicating a dedifferentiation in vitro modulated at the transcriptional level.
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000032:analysis; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D003593:Cytoplasm / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000378:metabolism; D006824:Hybridization, Genetic; D007073:Immunoglobulin E / Q000096:biosynthesis*; D009101:Multiple Myeloma / Q000032:analysis / Q000276:immunology*; D011132:Polyribosomes / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis*; D051381:Rats; D013997:Time Factors
chemical_list: D012333:RNA, Messenger; D012334:RNA, Neoplasm; D007073:Immunoglobulin E