Platelets are primarily associated with their main function, hemostasis, although it is known that these cells also exhibit
biological activity in
cancer progression,
inflammation and infectious processes. During
infection platelets, due to the expression of specific
receptors - Toll-like receptors (TLRs) - which recognize molecular patterns associated with pathogens -
pathogen-associated molecular patterns (
PAMPs) - are activated by the presence of microorganism components and/or substances released from damaged cells/tissue. Further antimicrobial activity of platelets is based on their capacity for phagocytosis, generation of
reactive oxygen species (ROS), and the synthesis, storage and release of
proteins/
peptides with antimicrobial activity. Another mechanism of platelet action is their immunomodulatory activity. It is based mainly on the ability to secrete
chemotactic factors allowing the accumulation of professional immunocompetent cells at the site of
infection, thus enhancing the effective eradication of an infectious agent. In
chronic infections, platelets, due to release of numerous
growth factors and various
cytokines, support mechanisms of acquired immunity. They accelerate the maturation of dendritic cells, stimulate B cells to be
immunoglobulin-producing plasma cells and potentiate the activity of T cells. Unfortunately, in certain situations (the existence of specific risk factors) the interaction of microorganisms with activated platelets may also be the cause of pathology within the cardiovascular system.