CD74 downstream cascade induces NF-κB activation. (A) 293 cells were transfected with FL CD74 or an empty plasmid, and their CD74 expression was determined by FACS analysis. (B-D) NF-κB activation was analyzed by luciferase assay, as described in “Materials and methods.” 293 cells transfected with FL CD74 (B,D) or the truncated 1-82 (C) constructs were stimulated with anti-CD74 or nonspecific antibodies (anti-CD8 or anti-RGS) in the presence (D) or absence (B-D) of the PI3K inhibitors wortmannin (wo) or LY 294002 (Ly) or the Syk inhibitor, piceatannol (pic) for 12 hours. Following the stimulation, the cells were lysed, and NF-κB activation was determined. The results shown represent the average of at least 5 independent experiments with similar results. Error bars represent the standard deviation of the results in the 5 experiments included.