THE INDUCTION OF PERSISTENCE OF I-A EXPRESSION BY MACROPHAGES FROM BCG(R) MICE OCCURS VIA A PROTEIN-KINASE C-DEPENDENT PATHWAY

We have described conditions by which MHC class II (I-A) glycoproteins can be induced to be differentially expressed after treatment of macr ophages with rIFN-gamma. Treatment of macrophages from BCG-resistant m ice with 1 U of rIFN-gamma induced transient I-A expression that decay ed in the presence of cycloheximide. Subsequent treatment of these mac rophages with 100 U of rIFN-gamma induced the persistence of I-A that was not affected by cycloheximide. The aim of this investigation was t o define, by pharmacologic intervention, the second signals that resul ted in the induction of the persistence of I-A. Treatment of the macro phages that transiently expressed I-A with PMA resulted in the inducti on of persistence. When we compared the effect of different protein ki nase C (PKC) inhibitors with the induction of persistence by rIFN-gamm a, we found that H-7 blocked the induction of persistence only when ad ded before or at the same time as the addition of a high dose of rIFN- gamma. In contrast, the addition of staurosporine to macrophages as la te as 2 h after treatment with high doses of rIFN-gamma inhibited the induction of I-A persistence. The addition of a high dose of rIFN-gamm a to macrophages previously treated with a low dose of rIFN-gamma resu lted in the synergistic activation of PKC. The effect of H-7 and of st aurosporine on the activation of PKC activity coincided with the effec t of these inhibitors on the induction of persistent I-A expression. T yrosine kinase inhibitors genistein and herbimycin did not affect the induction of I-A persistence nor of PKC activation. Antibody to the IF N-gamma receptor inhibited PKC activation. Finally, the addition of th e high dose of rIFN-gamma to macrophages from BALB/c.Bcg(s) mice, prev iously treated with the low dose of rIFN-gamma, failed to activate hig h levels of PKC activity attained after similar treatment of macrophag es from BALB/c.BCg(r) mice. One effect of the Bcg gene may be to regul ate the activation of PKC activity.