title: Reactivation of class II antigen expression in murine macrophage hybrids.
abstract: The induction of class II antigen on primary macrophages and on several macrophage cell lines has been demonstrated after exposure to IFN-gamma. The murine macrophage cell line PU5 (H-2d haplotype) does not express class II antigen constitutively and only trace levels are detected after induction with IFN-gamma. In an attempt to understand the nature of the defect in PU5, stable macrophage hybrids were derived by fusing a thymidine kinase-negative variant of PU5 with thioglycollate elicited peritoneal macrophages from CBA/J mice (H-2k haplotype). Hybrid clones isolated after HAT selection had approximately 35% more DNA than the PU5 parent suggesting that chromosomal loss had occurred post-fusion. While none of the hybrids expressed class II antigens of the k haplotype, constitutive expression of class II antigens of the d haplotype was detected by both micro-ELISA and by flow cytometry. Incubation of these hybrids with IFN-gamma resulted in a further increase in class II expression. Co-ordinate reactivation of both I-A and I-E antigens was observed in the PU5-macrophage hybrids. In contrast, although the IFN-gamma receptor on PU5 and the macrophage hybrids was indistinguishable by Scatchard analysis, neither intracellular class II antigen nor transcription of class II mRNA was detected in IFN-gamma-treated PU5. Reactivation was dependent on the PU5 fusion partner and was not related to a general post-fusion event as hybrids formed between PU5 and the murine fibroblast line A9 did not express class II antigen constitutively or after IFN-gamma induction.
mesh_terms: D000818:Animals; D002999:Clone Cells / Q000276:immunology / Q000378:metabolism; D003101:Collodion; D004591:Electrophoresis, Polyacrylamide Gel; D000949:Histocompatibility Antigens Class II / Q000032:analysis*; D006822:Hybrid Cells / Q000276:immunology* / Q000378:metabolism; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008808:Mice, Inbred CBA; D011233:Precipitin Tests; D011971:Receptors, Immunologic / Q000032:analysis; D017471:Receptors, Interferon
chemical_list: D000949:Histocompatibility Antigens Class II; D011971:Receptors, Immunologic; D017471:Receptors, Interferon; D003101:Collodion