L32

Question 1

What are the steps of the inflammatory response?

Answer 1

Chemical signals from tissue-resident cells act to attract more cells to the site of the injury.

Neutrophils enter the blood from the bone marrow and cling to the capillary wall near the site of inflammation.

Chemical signals from resident cells dilate blood vessels and make capillaries ‘leakier’

Neutrophils squeeze through the ‘leaky’ capillary wall and follow the chemical trail to the injury site.

Question 2

What are the stages of phagocytosis?

Answer 2

Phagocytes adheres to pathogens and forms psuedopods that engulf the particles forming the phagosome.

Then a lysosome fuses with the phagocytic vesicle forming a phagolysosome

Toxic compounds and enzymes destroy the pathogens.

And, sometimes exocytosis of the vesicle removes the indigestible and residual material

Question 3

What mechanisms cause the destruction and digestion of microbes in phagocytosis?

Answer 3

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

Question 4

What are the 3 complement pathway triggers?

Answer 4

Classical - Antibody bound to pathogen binds complement

Alternative - Pathogen binds complement to surface/pathogen component

Lectin - Carbohydrate components of microbes bind to complement

Question 5

What are the 3 outcomes of the complement cascade?

Answer 5

Label pathogens - opsonisation
Recruit phagocytes - Chemotaxis
Destroy pathogens - lysis

Question 6

What is a complement?

Answer 6

There are 9 major proteins/protein complexes (C1-9) which act in sequence to clear pathogens from blood and tissues

Question 7

What does C3b, C9 and C3a/C5a do in the complement cascade?

Answer 7

C3b - Labels pathogens which bind to complement receptors on phagocytes

C9 - Forms pores in membranes of bacterial cells causing death

C3a/C5a - Complement proteins act as peptide mediators of inflammation and recruit phagocytes

Question 8

What is opsonisation?

Answer 8

Coating of a microbe with antibody and/or complement fragment C3b to make microbe ‘tastier’ to phagocytes

Question 9

What is recruit?*

Answer 9

Phagocytes are attracted to site and mast cells are degranulated by C3a and C5a.
Inflammatory mediators released including proteins that attract phagocytes