Immunophilins and thrombotic disorders

The immunophilin family includes a large group of proteins with peptidyl prolyl-isomerase activity (PPI-ase). Immunophilins chaperone activity has been documented to be crucial for the correct folding and activation of many proteins. Thus, they have been subjected of intense investigation since they were firstly described in the last decades of the past century. Many of these studies have been focused on leukocyte constitutively expressed immunophilins, due to their relevance in the correct folding, and subsequently, sensitization and activation of the glycoprotein receptor (RGBs) of lymphocyte T CD4+ and Treg, hence regulating immunological responses against pathogen insults. Several clinical trials have been completed in the last decade reporting that administration of immunophilin-binding drugs, derived from macrolide lactones, like cyclosporine A (CsA) and tacrolimus (FK506), induced successful results in preventing organ rejection. By contrast, the expression of immunophilins and their physiological function remain poorly investigated in others cell types, such as platelets, where a reduced number of studies presenting evidences of immunophilins expression and their physiological contribution have been published, despite a number of clinical trials have noticed side effects of these drugs in thrombosis and platelet count, thus suggesting a possible regulatory function of immunophilins in human platelets, which is reviewed here.