12 Facts About Platelets

Platelets, called thrombocytes, are a component of blood whose function is to react to bleeding from blood vessel injury by clumping, thereby initiating a blood clot.

Platelets have no cell nucleus; they are fragments of cytoplasm that are derived from the megakaryocytes of the bone marrow or lung, which then enter the circulation.

Platelets participate in both innate and adaptive intravascular immune responses.

Platelets secrete thromboxane A2, which acts on the platelet's own thromboxane receptors on the platelet surface, and those of other platelets.

Platelets have central role in innate immunity, initiating and participating in multiple inflammatory processes, directly binding pathogens and even destroying them.

Platelets can bind to bacteria either directly through thrombocytic PRRs and bacterial surface proteins, or via plasma proteins that bind both to platelets and bacteria.

Platelets are rapidly deployed to sites of injury or infection, and potentially modulate inflammatory processes by interacting with leukocytes and by secreting cytokines, chemokines and other inflammatory mediators.

Platelets are the largest source of soluble CD40L which induces production of reactive oxygen species and upregulate expression of adhesion molecules, such as E-selectin, ICAM-1 and VCAM-1, in neutrophils, activates macrophages and activates cytotoxic response in T and B lymphocytes.

Platelets participate in chronic inflammatory diseases, such as synovitis or rheumatoid arthritis.

Platelets secrete proinflammatory and procoagulant mediators such as inorganic polyphosphates or platelet factor 4, connecting innate and adaptive immune responses.

Platelets collected by either method have a very short shelf life, typically five days.

Platelets do not need to belong to the same A-B-O blood group as the recipient or be cross-matched to ensure immune compatibility between donor and recipient unless they contain a significant amount of red blood cells.