Induction of assembly of MHC class I heavy chains with β2microglobulin by interferon-γ

Abstract

Assembly of histocompatibility class I heavy chains with β2microglobulin (β2m) is known to be necessary for cell surface expression. Studies on the H-2 class I deficient but interferon-γ (IFN-γ) inducible fibrosarcoma BC2 and the lung carcinoma CMT 64.5 showed that after transfection with allogeneic H-2 class I genes the class I proteins are expressed, but only intracellularly and not on the cell surface. In spite of the presence of β2m in the cells no association of the transfected class I chain with β2m was observed. However, stimulation with IFN-γ induced assembly and subsequent surface expression. These findings show that the assembly of class I heavy chains with β2m is not a spontaneous event but appears to be regulated by cellular mechanisms the nature of which is still unknown.