Cyclophilin B (SCYLP, CyPB and peptidyl-prolyl cis-trans isomerase B) is a 24 kDa glycoprotein member of the B subfamily of the cyclophilin-type PPIase family of molecules. It is both secreted and retained in the ER. When secreted, Cyclophilin B mediates chemotaxis and T cell adhesion to fibronectin. This is likely due to its prolyl cis/trans isomerase activity. Intracellularly, Cyclophilin B appears to serve as a molecular chaperone for molecules destined for secretion. It does so via stabilization, and facilitating the activity of additional chaperones.