Platelet Activation and Cytokine Detection: Unlocking the Secrets of Blood Cell Interactions
August 23 , 2024
Platelet activation plays a crucial role in primary hemostasis, which is the initial step in the physiological repair mechanism to prevent further bleeding when blood vessel walls are damaged. Platelet activation involves three processes: platelet adhesion, aggregation, and secretion. These processes lead to the formation of a platelet plug at the site of vessel injury, which is essential for primary hemostasis.
Platelet function
The functions of platelets mainly involve hemostasis and clot acceleration, while platelets also have the function of maintaining the integrity of capillary walls. In the process of hemostasis and clot formation, platelets have functions such as thrombus formation, wound blockage, and release of various factors related to coagulation. The average lifespan of platelets is 7-9 days, and aging and dying platelets are ultimately phagocytosed and processed by the spleen in the bloodstream.
The three processes of platelet activation:
1. Adhesion: Platelet adhesion is the attachment of platelets to non-platelet surfaces. When there is endothelial damage or activation of coagulation factors, platelets adhere to the subendothelial tissue. Components involved: The main protein involved in adhesion is platelet membrane glycoprotein GPIb. The subendothelial components consist mainly of collagen. The plasma von Willebrand factor (VWF) acts as a bridge for platelet adhesion. Process: Following vascular injury, collagen is exposed, and VWF binds to the exposed collagen. GPIb on the platelet membrane binds to the modified VWF, causing platelet adhesion to the collagen fibers. Defects in GPIb, VWF deficiency, or collagen fiber degeneration can result in bleeding.
2. Aggregation: Platelet aggregation is the clumping of platelets together. It involves fibrinogen, calcium ions (Ca2+), and the platelet membrane glycoprotein GP IIb/IIIa. Process: Activation by agonists exposes the fibrinogen receptor on GP IIb/IIIa molecules. Binding of fibrinogen to GP IIb/IIIa, facilitated by calcium ions, leads to platelet aggregation.Activated GP IIb/IIIa can also bind to VWF (secondary adhesion).
3. Release Platelet release refers to the phenomenon where platelets, upon stimulation, release substances stored within dense granules, alpha granules, or lysosomes. This process is also known as platelet secretion.
Platelet adhesion, aggregation, and release occur nearly simultaneously. Certain CD factors, serving as key proteins on the platelet membrane, facilitate the interaction between platelets and subendothelial tissues, fibrinogen, and other substances, thereby accelerating the processes of hemostasis and clotting. Together, they contribute to the physiological functions of hemostasis and clotting
What is the CD factor?
CD factors, also known as Cluster of Differentiation or differentiation antigens, refer to cell surface markers that appear or disappear during leukocytes' differentiation, maturation, and activation processes into different lineages and stages. They are a class of proteins or glycoproteins present on the cell membrane.
Human CD factors can be broadly divided into 14 groups: T cells, B cells, myeloid cells, NK cells, platelets, adhesion molecules, endothelial cells, cytokine receptors, activation antigens, carbohydrate antigens, dendritic cells, stem cells/progenitor cells, stromal cells, and red blood cells.
Platelet membrane glycoproteins (GPs) are specific glycoproteins produced after platelet activation. Over 10 types have been identified, including GPIb-IX-V, GPIa/IIa, GPVI, GPIIb/IIIa, P-selectin, and others. They serve as important mediators for platelet function. The expression level of platelet membrane glycoproteins reflects platelet activation status and is associated with various diseases. Measuring the expression of platelet membrane glycoproteins has become a novel approach for assessing platelet function, playing a crucial role in the diagnosis, treatment, and monitoring of platelet activation-related disorders.