We have reexamined 1B-6 cells, a cloned line of FRTL-5 rat thyroid cells in order to determine whether such cells demonstrate constitutive MHC class II gene expression. A new homologous cDNA probe for the RT1.D α-chain region was developed and proved significantly more sensitive at detecting specific mRNA levels in 1B-6 cells than a human class II α-chain specific probe used in previous studies. Recombinant rat γ-interferon induced MHC class II (RT1.D) antigen at concentrations as low as 1 U/ml (in the presence of bovine TSH), as detected by both α-chain specific mRNA transcripts and surface antigen expression. There was no evidence for constitutive expression of MHC class II transcripts in proliferating 1B-6 cells in the absence of γ-interferon, even when bovine TSH was present. These studies add further evidence to our hypothesis that MHC class II antigen expression in thyroid cells is secondary to external stimulating factors.
ASJC Scopus subject areas
- Molecular Biology