title: Human chromosome 21 determines growth factor dependence in human/mouse B-cell hybridomas.
abstract: Interleukin 6 (IL-6) serves as a growth factor for mouse plasmacytomas. As a model for IL-6-mediated growth of plasmacytomas, we study IL-6-dependent B-cell hybridomas, which can be generated through fusion of B lymphocytes with a plasmacytoma cell line, e.g., SP2/0. In the present report, we have investigated the peculiar behavior of B-cell hybridomas with respect to IL-6 dependence. We demonstrate that although newly generated hybridomas are IL-6 dependent, many hybridomas lose this dependency at frequencies as high as 50%, shortly after fusion. We speculated that the loss of IL-6-dependent growth is due to the well-known chromosomal instability of B-cell hybridomas. Consequently, loss of IL-6 dependence is the result of loss of a specific chromosome(s). This model implies the existence of an "IL-6 dependency" gene, the loss of which makes hybridomas capable of proliferating in the absence of IL-6. Because SP2/0 is IL-6 independent, the IL-6-dependent phenotype of B-cell hybridomas, and hence the IL-6 dependency gene, must be derived from the B lymphocyte. We have tested this model by generating human/mouse B-cell hybridomas through fusion of human B lymphocytes with SP2/0. We then analyzed the human chromosome content of 10 IL-6-dependent and 14 IL-6-independent subclones. From that analysis we concluded that the presence of human chromosome 21 correlated with IL-6 dependence. This correlation was confirmed by microcell fusion experiments in which a single copy of chromosome 21 was introduced into IL-6-independent hybridomas, resulting in reconstitution of the IL-6-dependent phenotype. We therefore conclude that chromosome 21 carries an IL-6 dependency gene.
authors.affiliation: Department of Autoimmune Diseases, Central Laboratory of The Netherlands Red Cross Transfusion Service, Academic Medical Center, University of Amsterdam. s.ebeling@lab.azu.nl
authors.forename: S B
authors.initials: SB
authors.lastname: Ebeling
authors.forename: H M
authors.initials: HM
authors.lastname: Bos
authors.forename: R
authors.initials: R
authors.lastname: Slater
authors.forename: W J
authors.initials: WJ
authors.lastname: Overkamp
authors.forename: A P
authors.initials: AP
authors.lastname: Cuthbert
authors.forename: R F
authors.initials: RF
authors.lastname: Newbold
authors.forename: M Z
authors.initials: MZ
authors.lastname: Zdzienicka
authors.forename: L A
authors.initials: LA
authors.lastname: Aarden
mesh_terms: D000818:Animals; D001402:B-Lymphocytes; D002455:Cell Division / Q000235:genetics; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics / Q000502:physiology*; D005260:Female; D006801:Humans; D006825:Hybridomas / Q000166:cytology; D015850:Interleukin-6 / Q000235:genetics* / Q000502:physiology; D007621:Karyotyping; D051379:Mice; D010641:Phenotype
chemical_list: D015850:Interleukin-6