key term - Collectins

Definition

Collectins are a group of calcium-dependent, collagen-containing lectins that play a crucial role in the innate immune system's chemical defenses against pathogens. They function as pattern recognition receptors, binding to specific carbohydrate structures found on the surfaces of various microorganisms.

5 Must Know Facts For Your Next Test

1. Collectins, such as mannose-binding lectin (MBL) and surfactant proteins A and D (SP-A and SP-D), are produced by the liver and various epithelial cells.
2. Collectins can activate the complement system, a cascade of proteins that helps eliminate pathogens and facilitate their removal by phagocytic cells.
3. Collectins can also directly agglutinate (clump) and neutralize microorganisms, inhibiting their ability to infect host cells.
4. Deficiencies or dysfunctions in collectin production or activity have been linked to increased susceptibility to certain infections and autoimmune disorders.
5. Collectins play a crucial role in the lung's defense against respiratory pathogens, where they help trap and clear inhaled microorganisms.

Review Questions

• Describe the primary function of collectins in the innate immune system's chemical defenses.
  • Collectins are a group of pattern recognition receptors that bind to specific carbohydrate structures on the surfaces of various pathogens, such as bacteria, viruses, and fungi. This binding triggers a series of immune responses, including the activation of the complement system, agglutination (clumping) of microorganisms, and facilitation of their removal by phagocytic cells. By recognizing and neutralizing these pathogens, collectins play a crucial role in the innate immune system's chemical defenses against infections.
• Explain the significance of collectin deficiencies or dysfunctions in relation to susceptibility to infections and autoimmune disorders.
  • Deficiencies or dysfunctions in collectin production or activity can lead to an increased susceptibility to certain infections, as the body's ability to recognize and eliminate pathogens is compromised. Additionally, dysregulation of collectin function has been linked to the development of autoimmune disorders, where the immune system mistakenly attacks the body's own tissues. This is because collectins play a delicate balancing act in the immune system, and their improper functioning can disrupt the fine-tuned balance between pathogen recognition, clearance, and self-tolerance.
• Discuss the role of collectins in the lung's defense against respiratory pathogens.
  • Collectins, such as surfactant proteins A and D (SP-A and SP-D), are particularly important in the lung's defense against respiratory pathogens. These collectins are produced by alveolar epithelial cells and help trap and clear inhaled microorganisms, preventing them from causing respiratory infections. Collectins can directly agglutinate (clump) pathogens, inhibiting their ability to infect host cells, and they can also activate the complement system to facilitate the elimination of these microorganisms. The crucial role of collectins in the lung's innate immune defenses highlights their importance in maintaining respiratory health and preventing pulmonary infections.

Related terms

Lectins: Proteins that bind to specific carbohydrate structures and play a role in various biological processes, including immune function.

Pattern Recognition Receptors (PRRs): Receptors that recognize conserved molecular patterns associated with pathogens, triggering an innate immune response.

Innate Immune System:

The body's first line of defense against infections, providing immediate, non-specific protection against a wide range of pathogens.