Complement inhibitors

Definition

Complement inhibitors are proteins that regulate the complement system, preventing excessive activation and protecting host tissues from damage. These inhibitors play a critical role in maintaining homeostasis and preventing autoimmune reactions by controlling the complement pathways, which can be activated through various triggers such as pathogens or immune complexes.

5 Must Know Facts For Your Next Test

1. Complement inhibitors can act at various stages of the complement activation pathways, including the classical, lectin, and alternative pathways.
2. Key complement inhibitors include proteins like Factor H, which inhibits C3 convertase activity, and CD59, which prevents the formation of the membrane attack complex (MAC).
3. Deficiency or dysfunction of complement inhibitors can lead to increased susceptibility to infections and autoimmune diseases due to uncontrolled complement activation.
4. Some pathogens have evolved mechanisms to evade the complement system by exploiting or mimicking complement inhibitors, enhancing their ability to survive in the host.
5. Complement inhibitors also play a role in therapeutic applications, as their modulation can help manage diseases characterized by excessive inflammation or autoimmunity.

Review Questions

• How do complement inhibitors function to prevent damage to host tissues during immune responses?
  • Complement inhibitors function by binding to various components of the complement system and blocking their activity. This prevents excessive complement activation that could lead to tissue damage or inflammation. By regulating key enzymes like C3 convertase and preventing the formation of harmful complexes, these inhibitors maintain a balance in immune responses and protect host tissues from unintended collateral damage.
• Discuss the consequences of deficiencies in complement inhibitors on human health and disease.
  • Deficiencies in complement inhibitors can lead to uncontrolled activation of the complement system, resulting in increased tissue damage and heightened risk of autoimmune diseases. For example, individuals with deficiencies in Factor H may develop conditions like atypical hemolytic uremic syndrome (aHUS), where excessive complement activation damages kidney cells. This demonstrates how crucial these inhibitors are for maintaining immune balance and preventing disease.
• Evaluate how pathogens might exploit complement inhibitors for their advantage and the implications for infection control strategies.
  • Pathogens can exploit complement inhibitors by either producing molecules that mimic these regulators or by hijacking host regulatory pathways. For example, some bacteria have surface proteins that resemble host complement inhibitors, allowing them to evade immune detection and survive longer within the host. This exploitation complicates infection control strategies because it not only enhances pathogen virulence but also challenges vaccine development efforts aimed at eliciting robust immune responses against these pathogens.

Related terms

Complement system: A complex network of proteins that play a crucial role in the immune response, facilitating opsonization, inflammation, and cell lysis.

C3 convertase: An enzyme complex formed during complement activation that cleaves C3 into C3a and C3b, initiating further complement cascade events.

Regulatory proteins: Proteins that modulate the activity of the complement system, including factors such as Factor H and CD55, which help to prevent damage to host cells.