Abstract: Objective　To construct eukaryotic expression vector carrying inducible co-stimulator (ICOS) Ig fusion gene, and investigate the ICOSIg expression in rat adipose tissue-derived mesenchymal stem cells (ADSCs). Methods　The encode of the extracellular domain of rat ICOS was cloned. The encode of the domain was fused with the gene of Fc     region encoding human immunoglobulin IgG, in order to build the ICOSIg fusion gene and the secreted eukaryotic expression vector pcDNA3.1(＋)/ICOSIg. After DNA sequence analysis, the recombinant plasmid was transfected into ADSCs, and the expression of ICOSIg was confirmed by Western blot analysis. Results　The sequencing confirmed that   pcDNA3.1(＋)/ICOSIg plasmid were successfully constructed, and ICOSIg was successfully expressed in ADSCs. Conclusion　The ICOSIg can be successfully expressed in ADSCs, which provides the experimental basis for further research on immune tolerance mechanism.

Key words: mesenchymal stromal cells, receptors, Fc, gene fusion, plasmids, inducible co-stimulator, eukaryotic expression vector, adipose tissue-derived mesenchymal stem cells