Updated project metadata. We used tyrosine phosphorylation profiling by anti-pTyr-antibody mediated enrichment and subsequent analysis by mass spectrometry in order to determine the changes in early signalling after mast cell activation. Mast cells were stimulated with varying concentrations of antigen for one minute and the differences between optimal (20 ng/ml) and supra-optimal (2000 ng/ml) antigen mast cell activation were analysed by nanoLC-MS/MS.