1. Sistem Komplemen- Classical

Summary

This video script explains the complement system in immunology, focusing on its role in microbial defense and inflammation. The complement system consists of over 30 proteins found in the serum and membrane-associated proteins. These proteins work together through a series of pathways (classical, lectin, and alternative) to initiate immune responses such as opsonization, inflammation, and pathogen lysis. The script details the activation of complement proteins like C1 to C9 and their interactions to combat infections, highlighting the importance of the liver in synthesizing these proteins and the immune system's role in recognizing and responding to invaders.

Takeaways

• 😀 Complement system consists of more than 30 proteins found in serum and associated with membranes, playing a vital role in immunity.
• 😀 Complement proteins include enzymes, coenzymes, and glycoproteins, which participate in various immune responses.
• 😀 The liver is the primary organ responsible for synthesizing complement proteins, contributing to immune function.
• 😀 The complement system is involved in inflammatory mechanisms, helping combat microbial infections.
• 😀 Complement proteins circulate in an inactive form and are activated when triggered by certain initiators like antigen-antibody complexes.
• 😀 There are three pathways to activate the complement system: classical, lectin, and alternative pathways, each initiated by different factors.
• 😀 Classical pathway activation occurs when antibodies (IgG or IgM) bind to antigens, which triggers the complement system.
• 😀 C1q, a key protein in the classical pathway, binds to antibodies, leading to a conformational change that activates proteases C1r and C1s.
• 😀 The classical pathway involves the activation of multiple complement proteins (C1 to C9), ultimately leading to the formation of membrane attack complexes (MAC).
• 😀 The MAC formed by complement proteins (C5b, C6, C7, C8, C9) creates pores in bacterial membranes, causing osmotic lysis of the pathogen.

Q & A

What is the complement system and its role in the immune response?

The complement system consists of over 30 proteins found in the serum and associated with membranes. It plays a crucial role in immune defense by helping to combat microbial infections, trigger inflammation, and enhance the ability of antibodies and phagocytic cells to clear pathogens.

How are complement proteins categorized?

Complement proteins are categorized into enzymes, coenzymes, and glycoproteins. These proteins are typically inactive and are activated in response to specific triggers, initiating the complement cascade.

What are the main pathways involved in the activation of the complement system?

The complement system can be activated through three main pathways: the classical pathway, the lectin pathway, and the alternative pathway. Each pathway is initiated by different factors, such as antigen-antibody complexes or pathogen surfaces.

What is the classical pathway in the complement system?

In the classical pathway, activation begins when antibodies (IgG or IgM) bind to antigens on a pathogen surface. This binding activates the C1 complex, leading to a cascade of reactions that ultimately results in pathogen destruction.

What role does the liver play in the complement system?

The liver is the primary organ responsible for the synthesis of complement proteins. These proteins are distributed in the extracellular fluid, including blood and interstitial fluid, and are essential for immune functions.

What is opsonization, and how does it work?

Opsonization is the process where opsonins, such as antibodies or complement proteins, coat pathogens, marking them for recognition and phagocytosis by immune cells. This enhances the ability of phagocytes to engulf and eliminate pathogens.

How is the complement system activated in the lectin pathway?

In the lectin pathway, activation occurs when lectin proteins, such as mannose-binding lectin (MBL), bind to specific carbohydrate structures on the surface of pathogens. This activates complement proteins and triggers a cascade similar to the classical pathway.

What happens after C3 convertase is formed?

Once C3 convertase is formed, it cleaves C3 into C3a and C3b. C3b then binds to pathogen surfaces and further activates the complement cascade, leading to the formation of C5 convertase, which ultimately leads to membrane attack complex formation.

What is the membrane attack complex (MAC), and how does it function?

The membrane attack complex (MAC) is a structure formed by complement proteins C5b, C6, C7, C8, and C9. It creates pores in the pathogen's membrane, causing cell lysis due to osmotic pressure and leading to the destruction of the pathogen.

What is the role of C5a and C3a in the inflammatory response?

C5a and C3a are small fragments produced during complement activation that act as chemotactic factors. They attract immune cells such as basophils and neutrophils to the site of infection, promoting inflammation and aiding in the immune response.