title: Up-regulated recombination-activating gene expression in sIg- variants of a human mature B cell line undergoing secondary Ig lambda rearrangements in cell culture.
abstract: To study the role of surface immunoglobulin (sIg) expression in the control of rearrangement activity at the Ig light chain loci, we established rare sIg- clones (lambda-) from a human sIg+ B cell line (mu lambda+). Upon expansion of these sIg- clones, surface immunofluorescence analysis revealed a gradual emergence of sIg+ subpopulations, differing from the original tumor cell line both in their idiotypes and C lambda isotypes. DNA analysis revealed that this sIg heterogeneity resulted from a process of ongoing Ig lambda rearrangements. That is, one of the Ig lambda rearrangements in the parental cell line was replaced by novel Ig lambda rearrangements in the sIg- clones, which in turn were replaced by yet additional Ig lambda rearrangements in the sIg+ variants. Northern analysis demonstrated that while the expression of the recombination-activating genes RAG1 and RAG2 was relatively low in the parental cell line, their expression was significantly increased in both the sIg- variants and their sIg+ progenies. We thus describe a human mature B cell line, in which differential RAG expression allows sIg heterogeneity to be generated through secondary Ig lambda gene rearrangements. Our results indicate that the induction of RAG expression may be inversely associated with sIg expression, but that sIg expression, alone, is not sufficient to down-regulate this expression.
authors.affiliation: Department of Immunology, University of Toronto, Canada.
authors.forename: N B
authors.initials: NB
authors.lastname: Stiernholm
authors.forename: N L
authors.initials: NL
authors.lastname: Berinstein
mesh_terms: D000483:Alleles; D001402:B-Lymphocytes / Q000276:immunology*; D004268:DNA-Binding Proteins; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D005796:Genes; D018398:Homeodomain Proteins; D006801:Humans; D007146:Immunoglobulin lambda-Chains / Q000235:genetics*; D066298:In Vitro Techniques; D009687:Nuclear Proteins; D011506:Proteins / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000032:analysis; D011995:Recombination, Genetic; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D007146:Immunoglobulin lambda-Chains; D009687:Nuclear Proteins; D011506:Proteins; C499311:RAG2 protein, human; D011947:Receptors, Antigen, B-Cell; C064655:V(D)J recombination activating protein 2; C064658:RAG-1 protein