Immunology Quiz: Complement System and Antibodies

<p>Two heavy chains and two light chains (A)</p> Signup and view all the answers

<p>By the J chain (B)</p> Signup and view all the answers

<p>Gram negative bacteria (C)</p> Signup and view all the answers

<p>Opsonization and phagocytosis (A)</p> Signup and view all the answers

<p>Plasma membrane (B)</p> Signup and view all the answers

<p>Gram negative bacteria are more readily lysed by MAC. (D)</p> Signup and view all the answers

<p>Facilitates pathogen recognition and uptake (D)</p> Signup and view all the answers

<p>Opsonization and phagocytosis (D)</p> Signup and view all the answers

<p>They enhance the effectiveness of antibodies and complements. (B)</p> Signup and view all the answers

<p>Toxin production (C)</p> Signup and view all the answers

<p>To target bacteria for phagocytosis. (B)</p> Signup and view all the answers

<p>All of the above (D)</p> Signup and view all the answers

<p>CR1 (C)</p> Signup and view all the answers

<p>Their capsules inhibit opsonization. (C)</p> Signup and view all the answers

<p>The activation of complement proteins. (C)</p> Signup and view all the answers

<p>1 molecule of C1q and 2 molecules of C1r and C1s (D)</p> Signup and view all the answers

<p>IgM (C)</p> Signup and view all the answers

<p>Binding to two Fc regions (D)</p> Signup and view all the answers

<p>They follow the same sequence after initial recognition (C)</p> Signup and view all the answers

<p>Binding of C5b to C6 (C)</p> Signup and view all the answers

<p>They activate and attract leukocytes (C)</p> Signup and view all the answers

<p>C9 (B)</p> Signup and view all the answers

<p>C5b678 binding to C9 (B)</p> Signup and view all the answers

<p>It cleaves C5 into C5a and C5b. (A)</p> Signup and view all the answers

<p>C5b (D)</p> Signup and view all the answers

<p>C5a (C)</p> Signup and view all the answers

<p>Soluble receptors (D)</p> Signup and view all the answers

<p>MASPs (A)</p> Signup and view all the answers

<p>Through the deposition of C3b on pathogen surfaces. (C)</p> Signup and view all the answers

<p>Classical pathway (B)</p> Signup and view all the answers

<p>C3b (B)</p> Signup and view all the answers

<p>Increased susceptibility to Neisserial infections (D)</p> Signup and view all the answers

<p>Complement Receptor 2 (CR2) (B)</p> Signup and view all the answers

<p>Vascular permeability and mast cell degranulation (B)</p> Signup and view all the answers

<p>Complement Receptor 1 (CR1) and Complement Receptor 4 (CR4) (B)</p> Signup and view all the answers

<p>Increased susceptibility to Neisserial infections (B)</p> Signup and view all the answers

<p>Regulating complement activation pathways (C)</p> Signup and view all the answers

<p>Phagocytosing foreign particles (B)</p> Signup and view all the answers

<p>Complement Receptor 3 (CR3) (B)</p> Signup and view all the answers

A complex of proteins assembled on the surface of bacterial membranes, ultimately forming a pore that leads to cell lysis.

The process of marking a pathogen for destruction by phagocytic cells.

The process of engulfing and destroying pathogens by immune cells.

The process of recruiting immune cells and other defense mechanisms to the site of infection.

The process of lysis by MAC is more effective against Gram-negative bacteria than Gram-positive bacteria.

Gram-negative bacteria have an outer membrane that is more susceptible to MAC attack.

The complement system is a critical part of the innate immune response.

Complement proteins can enhance the opsonization and phagocytosis of pathogens.

C3b is a protein fragment produced by the complement system. It attaches to the surface of bacteria, marking them for destruction by phagocytes.

Opsonization is the process of making a pathogen more recognizable to phagocytes by coating it with opsonins.

Phagocytosis is the process by which phagocytes engulf and destroy pathogens.

Opsonin is a molecule that binds to a pathogen and increases its chances of being phagocytosed.

Encapsulated bacteria are harder to phagocytose because they are surrounded by a capsule that protects them from phagocytes.

Gram-negative bacteria have an outer membrane that is more susceptible to MAC attack than the thick peptidoglycan layer of Gram-positive bacteria.

The MAC (Membrane Attack Complex) is a group of complement proteins that assemble on bacterial membranes, forming a pore that allows fluid and ions to enter, leading to cell lysis.

Antibodies (Ab) bind to antigens (Ag) to form immune complexes (ICs). These complexes can activate complement, which leads to the formation of MACs.

Complement is a system of proteins that plays a crucial role in the innate immune response. It helps in opsonization, phagocytosis, inflammation, and lysis of pathogens.

The Fab region of an antibody binds to the antigen. The Fc region binds to complement and Fc receptors on immune cells.

C5 convertase is the enzyme responsible for cleaving C5 into C5a and C5b.

C5 convertase is formed from C3 convertase by the addition of C3b, which binds to the C3 convertase complex.

C5a attracts neutrophils, which are immune cells that destroy invading microbes. This is one way the complement system signals the presence of infection.

C5b initiates the assembly of the Membrane Attack Complex (MAC). The MAC creates pores in the cell membranes of pathogens, ultimately leading to cell lysis.

The lectin pathway is a part of the complement system that is activated when soluble receptors recognize microbial surface patterns, initiating the cascade.

MASPs are serine proteases that cleave C4 and C2 proteins, starting the lectin pathway cascade. This is similar to how the classical pathway uses C1.

The lectin pathway can also be activated by cytokeratin, a protein found in the lining of blood vessels. When endothelial cells are damaged, this protein is exposed, and the lectin pathway is triggered.

MBL (Mannose-Binding Lectin) is the primary receptor involved in the lectin pathway, recognizing specific features on microbial surfaces.

The classical pathway of complement activation is initiated by the binding of C1q to two or more antibodies attached to an antigen.

IgM is the most effective antibody in activating the classical pathway because it can bind multiple C1q molecules simultaneously.

IgG can also activate the classical pathway, but it requires at least two IgG molecules to be close together to allow C1q to bind to both of them.

The Lectin and Classical pathways converge at the formation of the C3 convertase.

The MAC (Membrane Attack Complex) is formed from C5b, C6, C7, C8, and multiple C9 molecules. This complex forms a pore in the membrane of target cells, ultimately leading to lysis.

C5a and C3a are called anaphylatoxins because they trigger inflammation by increasing vascular permeability, recruiting leukocytes, and activating mast cells.

Anaphylatoxins like C5a and C3a act by binding to receptors on vascular endothelial cells and mast cells, leading to changes in vascular permeability and leukocyte recruitment.

The complement system uses a cascade of protein interactions to activate and amplify an immune response against pathogens. It plays a crucial role in both innate and adaptive immunity.

C3 deficiency is a serious condition where the body cannot produce enough C3, making it difficult to fight bacterial infections. This is due to the lack of opsonization and the ability to trigger the classical and alternative pathways of complement activation.

Deficiencies in late complement components hinder the formation of the MAC. This makes individuals more susceptible to bacterial infections caused by the Neisseria genus, especially Neisseria meningitidis (the cause of meningitis).

CR1 is a receptor found on phagocytic cells like macrophages and neutrophils. It binds to C3b and C4b, accelerating phagocytosis and enhancing the removal of immune complexes from the blood.

CR2 is found on B cells and follicular dendritic cells (FDCs). It binds to iC3b, C3dg, and C3d, helping to regulate the activation of B cells and the development of immune responses.

CR3 and CR4 are found on phagocytes and are involved in phagocytosis and cell adhesion. They bind to iC3b, further aiding in the clearance of pathogens.