Glucocorticoid-induced inhibition of Lck/Fyn enzymatic activity in vivo. Human PBMCs were isolated from whole blood obtained from 2 (no. 1, no. 2) healthy volunteers before and 1 hour after oral administration of 20 mg prednisolone. Next, cells were stimulated ex vivo for 15 minutes with anti-CD3 and anti-CD28 Abs and subjected to immunoprecipitation for Lck and Fyn. After performing in vitro kinase assays, lysates were analyzed on Western blot for SAM68 phosphorylation. Suppressed phospho-SAM68 expression in both Lck and Fyn immunoprecipitates was observed at 1 hour after prednisolone administration in both individuals. IB indicates immunoblotting; IP, immunoprecipitation.