Ppib, also known as peptidyl-prolyl cis-trans isomerase B, is a cyclosporine-binding protein and is mainly located within the endoplasmic reticulum. It is associated with the secretory pathway and released in biological fluids. This protein can bind to cells derived from T- and B-lymphocytes, and may regulate cyclosporine A -mediated immunosuppression. Recombinant mouse Ppib, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.