Lecture 3

Question 1

What do innate immune cells do

Answer 1

-They recognise and activated by pathogens
-They eliminate pathogens
-They communicate with other cells
-They activate and “steer” adaptive immune responses

Question 2

What are the 3 polymorphonuclear granulocytes

Answer 2

Basophils

Eosinophils

Neutrophils

Question 3

How much do PMNs make up in the blood

Answer 3

60-70%

Question 4

How long do PMNs live for

Answer 4

Live for 24 hours (short lived) but life is extended on entering tissues in response to chemoattractants

Question 5

What do PMNs have receptors for

Answer 5

C3b, IgG, IgA and they also recognise antibodies

Question 6

Principles of Eosinophils

Answer 6

-Few in the blood, but they’re also beneath mucous surfaces
-Receptors for C3b, IgG, IgA and IgE
-They release toxic proteins and free radicals that bind to components of pathogens and cause damage
-They defend against multicellular parasites
-role in allergy (asthma)

Question 7

Principles of Basophils

Answer 7

• Very few in blood

-Receptors for C3a, C5a, IgE and they bind to complement components

-When stimulated by pathogen, they release contents such as heparin and histamine

-They defend against parasites, induce inflammation and play a role in allergy

Question 8

Principles of mast cells

Answer 8

• They’re restricted to tissues (protect mucosal surfaces

-They have receptors for C3a, C5a and IgE

-They release contents of their granules: histamine and other mediators

-They’re sentinel- they alert the body in the first place that there’s an infection

Question 9

Principles of macrophages

Answer 9

Can be derived from monocytes during infection.

They’re long lived

Act as sentinel cells

Big eaters- can phagocytose 100 bacteria per cell

Receptors are C3b, IgG, IgA

They produce pro-inflammatory mediators

Question 10

Principles of dendritic cells

Answer 10

They’re found in skin and lymphoid tissues
They take up foreign materiel by phagocytosis/micropinocytosis
They digest foreign material and display fragments on their cell surface to t cells

Question 11

What are the stages of phagocytosis

Answer 11

1. bacterium binds to the surface of phagocytic cells. Antibody and complement aid binding
2. Phagocyte pseudopods extend and engulf the organism
3. invagination of phagocyte membrane traps the organism within a phagosome
4. A lysosome fuses and deposits enzymes into the phagosome. Enzyme cleaves macromolecules and generates reactive oxygen species, destroying the organism

Question 12

Examples of bactericidal agents

Answer 12

-Acidification
-Toxic oxygen-derived products
-Toxic nitrogen oxides
-Antimicrobial peptides
-Enzymes
-Competitors

Question 13

What are the most important mechanisms

Answer 13

Toxic oxygen derived products
Toxic nitrogen oxides

-These are very reactive and denature them
-Free radicals are short lived and are contained within vesicles so don’t damage body’s tissue

Question 14

What is an “oxidative burst”

Answer 14

Transient increase in oxygen consumption following phagocytosis due to activation of a membrane bound NADPH oxidase

Question 15

What are the stages of oxygen-dependent killing

Answer 15

-Activated NADPH oxidase converts O2 molecules to the superoxide ion O2-
-A second enzyme (super oxide dismutase) converts the superoxide to hydrogen peroxide
-Peroxidase enzymes and further convert hydrogen peroxide to hypo-chlorite ions and hydroxyl radicals

Question 16

Principles of NK cells

Answer 16

• They recognise “alerted self” from the changes in expression of self major histocompatibility type 1 proteins.
  -They’re important in viral and some intracellular bacterial infections until adaptive immunity is triggered
  -They have receptors for IgG
  -They’re also active against some cancer cells

Question 17

How do NK cells function

Answer 17

They induce apoptosis

Activated NK cells produce a pore forming protein (perforin) which inserts into the membrane of the infected host cell

Granule contents are released into the target and activate the apoptosis pathway