Cyclophilins: unexpected messengers in intercellular communications

Cyclophilins are abundant cellular proteins best known for their affinity for the immunosuppressive drug cyclosporin A. Until now, the physiological roles of cyclophilins were limited to intracellular functions. A recent paper by Allain and colleagues demonstrates that extracellular cyclophilin B specifically enhances chemotaxis and adhesion of the memory CD4+ T cells. This effect also requires glycosaminoglycans, thus adding cyclophilin B to other glycosaminoglycan-dependent factors that regulate leukocyte trafficking