The induction of class II antigen on primary macrophages and on several macrophage cell lines has been demonstrated after exposure to IFN-γ. The murine macrophage cell line PU5 (H-2(d) haplotype) does not express class II antigen constitutively and only trace levels are detected after induction with IFN-γ. 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-2(k) 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-γ 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-γ 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-γ-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-γ induction.
|Number of pages||6|
|Journal||Journal of Immunology|
|State||Published - 1988|