Effect of TNF-α on the MHC class I antigen-processing machinery is independent of IFN-γ activity.
(A) MHC class I up-regulation in 397 melanoma cell line treated with TNF-α is blocked by TNF-α–neutralizing antibodies. Levels of MHC class I expression in cells treated with TNF-α, alone or in the presence of either goat polyclonal TNF-α–neutralizing antibodies (designated anti-TNF) or unspecific goat IgGs, were monitored by flow cytometry. Level of MHC class I expression in each sample was compared to that in untreated cells, and the difference was expressed as MFI increase. Results of 1 of 2 representative experiments are shown. (B) MHC class I up-regulation in 397 melanoma cell line treated with TNF-α is not blocked by IFN-γ–neutralizing antibodies. Levels of MHC class I expression in cells treated with IFN-γ or TNF-α alone or in the presence of either rabbit polyclonal IFN-γ–neutralizing antibodies (designated anti-IFN) or unspecific rabbit IgGs were monitored by flow cytometry. Level of MHC class I expression in each sample was compared to that in untreated cells, and the difference was expressed as MFI increase. Results of 1 of 3 representative experiments are shown in the figure. (C) Expression of IFN-γ mRNA in BL, AA, and 397 tumor cells as assessed by RT-PCR. PCR products were separated on 1.6% agarose gel and visualized by ethidium bromide staining. Activated CD8+ CTL clone was used as a positive control for IFN-γ mRNA detection (P). Samples containing an aliquot of PCR-grade water were used as negative control (N). To control for RT and PCR amplification steps, β2-microglobulin mRNA was amplified from each sample.
