CHO cells were transfected with either Vector (pSRa) or expression vector driving expression of HCPTPA (pSRa-LMWPTP), and harvested in Triton X-100 lysis buffer at 72 h after transfection. 2mg of lysate protein was incubated for 1 h with 10ml of sheep-anti-LMWPTP containing anti-serum, and immunoprecipitated proteins recovered by Protein A/G were separated on PAGE (12%), and HCPTPA detected using a mouse antisheep monoclonal antibody.