Abstract
The article characterises platelets, pointing out the role and contribution of their numerous receptors determining their specific and broad immune activity. Three types of platelet receptors are described, that is, extracellular and intracellular receptors-TLR (toll-like receptors), NLR (NOD-like receptor), and RLR (RIG-I-like receptor); extracellular receptors-selectins and integrins; and their other extracellular receptors-CLR (C-type lectin receptor), CD (cluster of differentiation), TNF (tumour necrosis factor), among others. Outlining the contribution of these numerous platelet receptors to the intravascular immunity, it has been shown that they are formed by their fusion with pathogen-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), and lifestyle-associated molecular patterns (LAMPs). They are initiating and effector components of signal transduction of these cells, and their expression and quantity determine the specific and broad functions of platelets towards influencing vascular endothelial cells, but mainly PRRs (pattern recognition receptors) of blood immune cells. These facts make platelets the fundamental elements that shape not only intravascular homeostasis, as previously indicated, but they become the determinants of immunity in blood vessels. Describing the reactions of the characterised three groups of platelet receptors with PAMP, DAMP and LAMP molecules, the pathways and participation of platelets in the formation and construction of intravascular immune status, in physiological states, but mainly in pathological states, including bacterial and viral infections, are presented, making these cells essential elements in the health and disease of mammals, including humans.