opsonised

Opsonic is a term used in immunology to describe a substance that enhances the ability of phagocytes, such as macrophages and neutrophils, to recognize and engulf pathogens or other foreign particles. This process is known as opsonisation. Opsonins act as molecular bridges, coating the surface of a target particle and displaying specific binding sites for receptors on the surface of phagocytes.

The most common opsonins in the body are antibodies, particularly IgG, and complement proteins, such as C3b. Antibodies bind to antigens on the surface of the pathogen. The Fc portion of the antibody then becomes accessible to Fc receptors on phagocytes, facilitating phagocytosis. Complement proteins can also bind directly to pathogens or be coated by antibodies, and their presence signals to phagocytes to engulf the opsonised particle.

Opsonisation is a crucial mechanism of the innate and adaptive immune systems. It significantly increases the efficiency of phagocytosis, ensuring rapid clearance of invading microorganisms and cellular debris. Without opsonisation, phagocytes would have a much harder time binding to and removing potential threats, making the body more susceptible to infection. The process can be both natural, occurring as part of the body's defense, and induced, for example, through vaccination.