Effect of protein kinase inhibitors on physiological and PMA potentiated responses to IFNg. Expression levels of MHCII induced by 1,000 IU/ml IFNg alone are indicated by triangles (▲). Expression levels of MHCII induced by combined treatment with 1,000 IU/ml IFNg, 1,000 ng/ml PMA and 172 mM ethanol are indicated by squares (■). IFNg and PMA were added after cells had been pretreated with Staurosporine and GF 109203X for 1 hr. Incubation continued for the next 24 hr in the constant presence of inhibitors. Physiological response to IFNg in SW480 colon carcinoma cells was abrogated by 1 μM Staurosporine. PMA-potentiated response to IFNg in LS1034 colon carcinoma cells was abrogated by 100 nM Staurosporine or by 1 μM GF 109203X. Mean values of two independent experiments are plotted.