opsonin binding

Definition

Target type: molecularfunction

Binding to an opsonin, such as a complement component or antibody, deposited on the surface of a bacteria, virus, immune complex, or other particulate material. [GOC:add, ISBN:0781735149]

Opsonin binding is a crucial process in the innate immune system, where molecules known as opsonins bind to the surface of pathogens, tagging them for destruction by phagocytes. These opsonins act as "eat me" signals, facilitating the recognition and engulfment of pathogens by immune cells.

The process of opsonin binding involves several steps:

1. **Opsonin Recognition:** Opsonins, such as antibodies, complement proteins, or collectins, bind specifically to the surface of pathogens. Antibodies recognize specific antigens on the pathogen's surface, while complement proteins bind to pathogen-associated molecular patterns (PAMPs). Collectins, like mannose-binding lectin, bind to sugar molecules present on bacterial surfaces.

2. **Opsonin-Pathogen Complex Formation:** Once opsonins bind to the pathogen, they form a complex that can be recognized by phagocytic receptors on immune cells.

3. **Phagocyte Recruitment:** Opsonized pathogens can attract phagocytes to the site of infection through chemotaxis.

4. **Phagocytosis:** Phagocytes, such as neutrophils and macrophages, possess receptors that recognize opsonins bound to pathogens. These receptors bind to the opsonin-pathogen complex, triggering the engulfment of the pathogen into a phagosome.

5. **Pathogen Degradation:** Once inside the phagosome, the pathogen is degraded by various enzymes and reactive oxygen species produced by the phagocyte.

Opsonin binding is essential for effective immune defense by:

* **Enhanced Phagocytosis:** Opsonization significantly increases the efficiency of phagocytosis, leading to rapid clearance of pathogens.
* **Complement Activation:** Some opsonins, like complement proteins, can activate the complement cascade, leading to the formation of the membrane attack complex (MAC), which can directly lyse pathogens.
* **Immune Cell Activation:** Opsonized pathogens can activate immune cells, leading to the production of cytokines and other inflammatory mediators that contribute to the immune response.

Opsonin binding plays a critical role in protecting the host from a wide range of pathogens, including bacteria, viruses, and parasites. Understanding the molecular mechanisms of opsonin binding is crucial for developing new therapeutic strategies to enhance immune responses and combat infections.'
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Proteins (1)

Compounds (22)