Signal transduction in B lymphocytes

We have examined the activity and intracellular compartmentalization of protein kinase C (PKC) following activation of human B lymphocytes by anti-human leukocyte antigen (HLA) class II antibodies. 12-O-Tetradecanoylphorbol 13-acetate (TPA) treatment increased membrane-associated PKC (between five and nine times greater than the control value) and decreased cytosolic PKC (between 70% and 100% of the control value). In contrast, anti-class II antibodies induce an activation of PKC which results either in an increase of cytosolic activity or membrane-bound activity without redistribution of cytosolic PKC. The effect of TPA and HLA class II molecules on total PKC activity was comparable: when TPA induced an increase of total PKC activity so did HLA class II molecules and when TPA did not, HLA class II molecules did not. Measurement on SDS PAGE of histone phosphorylation confirmed the above results of PKC activity. Taken together, our results suggest that PKC might be implicated in HLA class II-induced B lymphocyte activation.