Tyrosine phosphorylation of cellular proteins and expression of SHP-1, SHP-2, and CD45 in normal (N) and PV ECFC. Day-6 ECFC were collected from suspension cultures, washed with phosphate-buffered saline, and lysed in buffer A with 1% Triton X-100. Equal amounts of extracts (25 μg) were subjected to SDS-PAGE and analyzed with antiphosphotyrosine (left panel) or the indicated anti-PTP antibodies (right panel). Purities of the ECFC were 75% and 70% for normal and PV samples, respectively. A representative figure from three experiments with similar results is shown. Each experiment was performed with blood samples from different normal volunteers and PV patients.