The observation that interferon (IFN) therapy causes regression of lesions in some patients with recurrent respiratory papillomatosis (RRP) raises the possibilities that these patients may have abnormalities in endogenous IFN production or in antitumor immune responses stimulated by IFN. We have measured IFN production and natural cytotoxicity (NK activity) in nine patients with RRP, three of whom were receiving exogenous IFN at the time of testing. Production of IFN- induced by the T cell mitogen Staphylococcus enterotoxin A was normal in all patients. Production of IFN-α induced by two viruses (Sendai and Newcastle disease viruses) was normal in the six untreated patients, but significantly lower in the patients on IFN therapy. Natural cytotoxicity against K562 target cells, both spontaneous and IFN-stimulated, was normal in all RRP patients tested. Thus, we have shown that the NK-IFN system was intact in untreated patients with RRP. IFN-α production in the RRP patients on IFN therapy was low. The significance of these findings is discussed.
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