Lecture 32

Question 1

What are the 3 layers of immune defense?

Answer 1

Physical and chemical, innate and adaptive.

Question 2

What attracts more cells to the site of injury?

Answer 2

Chemical signals from tissue-resident cells acts to attract more cells to the site of injury or infection

Question 3

Where does neutrophils enter the blood from?

Answer 3

Bone marrow

Question 4

Do neutrophil cling to the capillary wall?

Answer 4

Yes

Question 5

What causes blood vessels to dilate and make capillaries to become leakier?

Answer 5

Chemical signals from tissue-resident cells dilate blood vessels and make capillaries leakier

Question 6

What happens in an inflammatory response when there is a cut in the skin?

Answer 6

• Chemical signals from tissue-resident cells act to attract more cells to the site of injury
• Neutrophils enter blood from the bone marrow
• Neutrophils cling to the capillary wall
• Chemical signals from tissue-resident cells dilate blood vessels and make capillaries ‘leakier’
• Neutrophils squeeze through the leaky capillary wall and follow the chemical trait to the injury site

Question 7

What is phagocytosis?

Answer 7

A process by which blood could ingest and destroy microbes

Question 8

What is the stages of phagocytosis?

Answer 8

1. Phagocyte adheres to pathogens or debris
2. Phagocyte forms pseudopods that eventually engulf the particles, forming a phagolysosome
3. Lysosomes fuses with the phagotic vesiscle forming a phagolysosome
4. Toxic compounds and lysosomal enzymes destroy pathogens
5. Sometimes exocytosis of vesicle removes indigestible and residual material.

Question 9

How do phagocytes kill microbes? What do they use?

Answer 9

• Low pH- Acid environment
• Reactive oxygen (hydrogen peroxide) and reactive nitrogen intermediates (nitric oxide)
• Enzymes such as proteases, lipases and nucleases

Question 10

What is a complement made out of and what does a complement do?

Answer 10

9 major proteins/ protein complexes act in sequence to clear pathogens from blood and tissues

• Label pathogens (opsonisation)
• Recruit phagocytes (chemotaxis)
• Destroy pathogens (lysis)

Question 11

What are the 3 complement pathways and describe them

Answer 11

Classical- Antibody bound to pathogen binds complement
Alternative- Pathogen binds complement to surface/ pathogen component
Lectin - Carbohydrate components of microbes bind complement

Question 12

What happens when complement pathways converge?

Answer 12

Amplification - C3 Convertase (enzyme complex)

Outcomes- Label, destroy and recruit

Question 13

What is label in the complement cascade?

Answer 13

Opsonisation ( Labels pathogens which bind to complement receptors on phagocytes)/ coating of a microbe with antibody and/or complement fragment C3b

Question 14

What is destroy in the complement cascade?

Answer 14

Membrane attack complex formation: pores in bacterial cells –> death C9/ Microbes coated with C3b are phagocytosed, assembly of MAC complex causes lysis

Question 15

What is recruit in the complement cascade?

Answer 15

Complement proteins act as peptide mediators of inflammation and recruit phagocytes/ phagocytes are attracted into site, mast cells degranulated by C3a and C5a, inflammatory mediators released including proteins that attract phagocytes