Tyrosine kinase activity of Syk in lysates of 32D cells transfected with WT or MT G-CSF-R. 32D myeloid cells transfected with WT G-CSF-R or the truncated MT G-CSF-R were stimulated for 10 minutes with hG-CSF and then lysed. Cell lysates were immunoprecipitated with anti-Syk antibody. Activation of Syk kinase was analyzed in immunoprecipitates. Results obtained using nonradioactive kinase assays are expressed as picomoles phosphate. Results represent the means of triplicate experiments. Error bars represent SD.