FIGURE 4.

IFN-γ decreases phosphorylation of select EGFr tyrosine residues. Cells were treated for 48 h with IFN-γ or control, and phosphorylation of five key tyrosine residues was analyzed by Western blot. Densitometric analysis revealed a significant decrease in phosphorylation of EGFr residues Tyr¹⁰⁶⁸ and Tyr¹⁰⁸⁶ at 15 min after EGF stimulation (a and b; **, p ≤ 0.01 (n = 7); ***, p ≤ 0.001 (n = 8)) in cells treated with IFN-γ. Phosphorylation of Tyr⁹⁹² was delayed in IFN-γ-treated cells (c, n = 14, not significant), whereas that of Tyr¹¹⁴⁸ and Tyr¹¹⁷³ was reduced slightly but not significantly (d and e, n = 15 and n = 5, not significant). Error bars, S.E.