complement cascade

Question 1

Name the 3 responses of the complement cascade

Answer 1

recruitment of inflam. cells, opsonization of bacteria, and killing of pathogens

Question 2

Define recruitment of inflam. cells

Answer 2

Dendrites - present antigens to t cells

chemotaxis - movement of white blood cells to its place of action

Question 3

Opsonization of bacteria

Answer 3

The process of opsonization begins when the immune system recognizes a particle (e.g., a bacterium) as an invader. The recognition stimulates the production of antibodies that are specific for the antigenic target. Certain antibody molecules are stimulated to bind to the surface of the particle. Typically, the binding molecules are a type of antibody classified as IgG. As well, proteins involved in the complement-mediated clearance of foreign material, specifically a protein designated C3b, can bind to the surface of the foreign object. Proteins such as IgG and C3b, which can promote opsonization, are designated as opsonins.When the IgG antibodies bind to the invading bacterium, the binding is in a specific orientation. An antibody is somewhat “Y” shaped. The binding of IgG to the bacterium is via the branching arms of the “Y.” The stalk of the molecule, which is termed the Fc region, then protrudes from the surface. The Fc region is recognized by a receptor on the surface of an immune cell called a phagocyte. When the Fc region is bound to the phagocytic receptor the invading particle is taken into the phagocyte and enzymatically digested.

The Cb3 complement protein can bind in a nonspecific manner to an invading particle. Phagocytes also contain surface receptors that recognize and bind Cb3. As with IgG, the binding of Cb3 to the phagocytes triggers a process whereby the invading particle is engulfed, surrounded, and taken inside the phagocytic cell for destruction.. Neutrophils and macrophages are involved.

Question 4

killing of pathogens

Answer 4

phagocytosis, apoptosis

Question 5

Name the 3 pathways of the complement cascade

Answer 5

Classical, lectin and alternativee

Question 6

What triggers the classical pathway

Answer 6

The classical pathway is triggered by activation of the C1-comple

Question 7

What triggers the lectin pathway

Answer 7

This pathway is activated by binding of MBL to mannose residues on the pathogen surface

Question 8

What trggers the alternative pathway

Answer 8

Hydrolysis of c3 and binding to pathogen surfaces