Expression and bioactivity of the fusion gene between extracellular portion of human ICOS and Fc portion of mouse IgG 2a / 中国免疫学杂志

ABSTRACT

Objective:To produce a fusion protein(ICOS-Ig)between extracellular portion of human ICOS and Fc portion of mouse IgG 2a and study on its biological activity.Methods:cDNA encoding the extracellular domain of human ICOS was prepared by RT-PCR from the RNA of the stimulated human peripherial blood mononuclear cells. The Fc portion of mouse IgG2a was cloned by PCR from the vector that contains the sequence-encoding Fc portion of mouse IgG2a.Two resulting amplified PCR products were ligated into a secrection mammalian expression vector, pSecTag2/Hygro A. The recombined vector was transfected into CHO cells by lipofectamine2000.Results:RT-PCR demonstrated the integration and mRNA synthesis of fusion gene. ELISA and Western blot analysis showed the expression of ICOS-Ig and its molecular weight was between 43-66 kD, its concentration was 5-25 ?g/ml. FACS analysis assured that ICOS-Ig had ligand specific binding activity. Addition of ICOS-Ig to MLR resulted in inhibition of T-cell proliferation and IL-2,IFN-? secretion.Conclusion:The fused gene ICOS-Ig was constructed and expressed successfully. It had the bioactivity of inhibition of T cell proliferation and cytokine secretion.