The tyrosine protein phosphatase, SHP-1, is equally expressed in HCD57, HCD57-SREI cells and primary human erythroid cells. Frozen HCD57 and HCD57-SREI cells were sent to Dr Amittha Wickrema who compared 10 μg of total cellular protein from these cell lines with an equal amount of primary erythroid cells at the CFU-E stage of development that develop in culture from more immature erythroid cells purified from human blood. The Western blot was probed with anti–SHP-1 antiserum and visualized by ECL.