Cyclophilin A (CYPA) is a member of the cyclophilins family, which is characterized by single peptide chains with peptidyl-prolyl cis-trans isomerase activity. CYPA is widely distributed in the cytoplasm and nucleus, participating in protein folding, cell signal transduction, and immune regulation. By binding to cyclosporine, CYPA affects the activity of calcineurin, thereby regulating T cell activation and immune responses. The expression of CYPA is specific in different tissues and cells, and mutations or dysregulation in its gene expression are associated with the occurrence and development of various diseases, including inflammation, infection, and cancer.