Increased expression of MHC class I molecules on human cells after short time IFN-γ treatment

Human cell lines and blood lymphocytes were treated for short time periods with IFN-γ. This treatment increased the amount of the assembled MHC class I molecules on the plasma membrane after 30 min. This early increase of the membrane expression subsided in the next few hours. A second wave of elevation occurred after 8–24 hr. Analysis of cytoplasmic and membrane molecules in pulse chase experiments showed that the cytokine enhanced both the assembly of available heavy and light chains and the transport of the complex to the plasma membrane. The membrane level of the HLA-A2 molecules showed similar kinetics. Addition of an A2 specific binding peptide stabilized the IFN-γ induced molecules on the cell surfaces. It seems that IFN-γ alone or together with a binding peptide can influence MHC class I expression solely through post-transcriptional events utilizing an available pool of free heavy and light chains already after a short time, before the enhancement of the synthesis starts.