Both antigen and KL stimulate activating phosphorylations of the MAP kinases and Akt. Human mast cells were incubated overnight in the presence of antigen-specific IgE either in the absence (Deprived Cells, A) or presence (Nondeprived Cells, B) of KL and IL-6. Cells were left unstimulated or stimulated with 100 ng/mL KL, antigen (Ag), or both for 15 minutes in panel A or with antigen for the times indicated in panel B. Proteins were immunoblotted with antibodies that detect the activated phosphorylated forms of the MAP kinases and Akt (designated with the prefix “p-”). Similar results were obtained in 2 other experiments.