L21

Question 1

What is the Immune System?

Answer 1

A system of cells and molecules that work

together to fight invading pathogens

Question 2

Molecules of the immune system and their main functions: (6)

Answer 2

• Antibody (Ab) – eliminates antigen (Ag)
• Complement – stimulates inflammation
• Cytokines – intercellular communication
• Adhesion molecules – cellular localisation
• Microbicidal compounds – kill microorganisms
• Apoptosis-inducing proteins – kill infected cells

Question 3

Molecules of the immune system and their main functions: (6)

Answer 3

• Antibody (Ab) – eliminates antigen (Ag)
• Complement – stimulates inflammation
• Cytokines – intercellular communication
• Adhesion molecules – cellular localisation
• Microbicidal compounds – kill microorganisms
• Apoptosis-inducing proteins – kill infected cells

Question 4

Molecules of the immune system and their main functions: (6)

Answer 4

• Antibody (Ab) – eliminates antigen (Ag)
• Complement – stimulates inflammation
• Cytokines – intercellular communication
• Adhesion molecules – cellular localisation
• Microbicidal compounds – kill microorganisms
• Apoptosis-inducing proteins – kill infected cells

Question 5

Pathogen recognition by immune

system cells: Phagocyte

Answer 5

Receptor specific for a molecule associated with several different pathogens
e.g. Toll-like receptor 5 (TLR5) recognising bacterial flagellin

Question 6

Pathogen recognition by immune

system cells: Lymphocyte

Answer 6

Receptor specific for a molecule often unique to a given pathogen:
T-cell receptor [TCR] (on T-cells) and
transmembrane antibody [BCR] (on B-cells)

Question 7

Killing of a bacterium following activation of a PHAGOCYTIC cell: (8)

Answer 7

1. Chemotaxis
2. Adherence via PAMP recognition
3. Cell activation via pathogen recognition receptor
4. Initiation of phagocytosis
5. Phagosome formation
6. Phagolysosome formation
7. Bacterial killing and digestion
8. Release of degradation products

Question 8

Summary:

Answer 8

• Cells of the immune system have receptors for pathogens
• The immune system cells need to get to the site of the infection
• They need to be activated to carry out their function
• A broad range of effector functions can lead to destruction of the pathogen