Synergy between interferons and monokines in MHC induction on brain endothelium

Rat brain endothelial cells were cultured as confluent monolayers and stimulated with combinations of interferon-beta (IFN beta), interferon-gamma (IFN gamma), tumour necrosis factor (TNF) and interleukin 1 (IL-1). After 4 days of stimulation the cell surface expression of class I and class II MHC molecules was quantitated by enzyme immunoassay. TNF by itself enhances class I expression and it synergises with IFN gamma in enhancing class I expression and inducing class II. IL-1 does not affect class I expression, nor does it synergise with IFN gamma in this respect. High doses of IL-1 slightly reduce IFN gamma mediated class II induction, but have no synergistic effect at lower doses. IFN beta stimulates class I weakly and induced class II in one experiment but the effects seen when IFN gamma and IFN beta were used together were additive, not synergistic. IFN gamma is the most potent modulator of MHC expression on these cells, although TNF acts as a strong co-stimulator, while IL-1 and IFN beta have only minor effects.