[The extracellular segment of mouse soluble SIRPα enhances the phagocytosis of macrophages to L1210 leukemia cells].

Objective To study the role of mouse extracellular segment protein of signal-regulatory protein α gene (mSIRPα) of mice in tumor immune regulation by cloning mSIRPα, constructing its prokaryotic expression vector and achieving the soluble expression of SIRPα. Methods The mSIRPα gene was amplified from mouse lymph node and the prokaryotic expression vector of pET32a-SIRPα was further constructed. After the soluble expression of recombinant Trx-mSIRPα fusion protein containing thioredoxin (Trx) tag was achieved, mouse bone marrow-derived monocytes were cultured and induced to differentiate into macrophages. Then the macrophages were co-cultured with L1210 leukemia cells labeled with 5(6)-carboxyfluorescein diacetate succinimide ester (CFSE). Trx-mSIRPα protein and Trx control protein were added into the co-culture system. The role of recombinant protein in the macrophage phagocytosis of tumor cells was observed by immunofluorescence cytochemical staining and confocal microscopy. Results Purified soluble Trx-mSIRPα protein was obtained and it was showed that it could enhance the phagocytosis of macrophages in mouse L1210 leukemia cells in vitro phagocytosis experiments. Conclusion Prokaryotic expression of Trx-mSIRPα protein can effectively enhance the phagocytosis of macrophages in leukemia cells, thus playing the role of anti-tumor immunotherapy.