Innate immunity

Question 1

What are some examples of chemical barriers to infection?

Answer 1

• Acid in the stomach
• Mucus on the surface
• antimicrobial properties e.g defensins which are secreted at the epithelial surface

Question 2

What is the function of the innate barriers of infection

Answer 2

To prevent pathogens from gaining access to the deep tissues

Question 3

What do epithelial layers produce?

Answer 3

They produce protective substances
* acidic pH
* enzymes and binding proteins
* antimicrobial peptides

Question 4

What are sentinel cells?

Answer 4

Resident tissue cells that detect invasion by recognising DAMPS and PAMPS
they can then send signals to initiate a response to
* dendritic cells
* Macrophages
* Mast Cells
*

Question 5

What kind of cells develop from myeloid progenitor cells?

Answer 5

• Red blood cells
• Monocytes
• Megakaryocytes
• Granulocytes

Question 6

What kidn of cells develop from lymphoid progenitor cells

Answer 6

• T cells
• B cells

Question 7

What is the precurser to macrophages and dendritic cells?

Answer 7

Monocytes

Question 8

What is the function of dendritic cells?

Answer 8

Important bridge between innate and adaptive immunity
can act as APC’s

Question 9

What kind of cells do NK cells kill?

Answer 9

any virus infected or abnormal cell that fails to express MHC Class I molecules

Question 10

What kind of cells are MHC I molecules usually present on?

Answer 10

all nucleated cells of the body

Question 11

What do MHC class I receptors do when they bind to NK cells?

Answer 11

switch off their ‘killing abilities’

Question 12

What is the definition of phagocytosis?

Answer 12

engulfment and internalisation of materials such as microbes for their clearance and destruction

Question 13

What are the two different receptors that are found on phagocytes (recognise microbes)

Answer 13

• Pattern recognition receptors- bind to the LPS of bacteria
• Opsonin receptors, e.g immunoglobulin FC receptors- bind to iG + AG

Question 14

What is the definition of the complement system?

Answer 14

A group of serum proteins circulating in inactive form

Question 15

What systems activate the complement system?

Answer 15

Both the adaptive (classical pathway) and the innate immune system ( alternative pathway)

Question 16

What are the possible outcomes after the complement system is activated?

Answer 16

• Targets cell lysis
• Chemotaxis
• Opsonisation to enhance phagocytosis

Question 17

What are the three activation pathways that are part of the complement system?

Answer 17

• Classical
• Lectin
• Alternative

Question 18

What is the classical activation pathway

Answer 18

requires the interaction of an antibody with a specific antigen

Question 19

What is the lectin activation pathway?

Answer 19

PAMPS recognition by lectin receptors

Question 20

What is the alternative activation pathway?

Answer 20

activation of the complement via the microbe itself

Question 21

What is the function of cytokines?

Answer 21

• coordinate an effective immune response
• Moderate the communication between lymphocytes, inflammatory cells
  and haematopoietic cells.
• additional roles separate from the immune system in developmental
  processes such as
• cell differentiation
• directed migration.

Influencing both innate and adaptive immune responses

Question 22

What are some of the different families of cytokines?

Answer 22

• Pro-inflammatory cytokines
• Chemokines
• Inteferons

Question 23

Where do defensins sit?

Answer 23

They sit in the lipid bilayer

Question 24

What two cells are examples of monocytes?

Answer 24

Macrophages and dendritic cells

Question 25

How many populations of innate lymphoid cells are there?

Answer 25

at least four * ILC1- found in large numbers in the intestinal wall * ILC2- scattered throughout the body and secrete cytokines * ILC3- act like TH17 cells and promote inflammation by releasing TH17 * ILC4 natural killer cells

Question 26

How do defensins work?

Answer 26

They can directly kill or inhibit the growth of microorganisms

Question 27

What are the two phagocytic cells?

Answer 27

Neutrophils and Macrophages

Question 28

What are the innate lymphoid cells?

Answer 28

* Cytokine secreting ILC's * Cytotoxic ILC-NK cells

Question 29

How do the leukocytes get where they are required?

Answer 29

1. Macrophages produces cytokines such as TNF-alpha and IL-1 2. TNF-alpha, IL1 and other chemokines activate selectins 3. The force of blood flow causes leukocytes to roll 4. Chemokines produced in the surrounding tissues bind to the rolling leukocytes in a high affinity state 5. Leukocytes can crawl to junctions and migrate through the wall (diapedesis)

Question 30

What are the functions of the natural killer cells?

Answer 30

* They can kill virus-infected or other 'abnormal' cells that fail to express MHC class I molecules * If MHC I binds to a natural killer cell it 'switches off' the killing abilities

Question 31

What happens when certain viruses and tumours 'down regulate' the expression of the MHC class I molecules?

Answer 31

The natural killer cells bind to the virus-infected target cells, inject them with proteins to induce cell death and thus eliminate the virus-infected cells

Question 32

Give some examples of antimicrobial phagocytic mechanisms

Answer 32

* Toxic Nitrogen oxides- NO * Enzymes- Lysozyme (digests the cell wall of gram-positve bacteria) * Antimicrobial peptides- Cathelicidin in macrophages, defensins in neutrophils

Question 33

How does the classical pathway begin?

Answer 33

Antibodies binding to antigens, Cleavage of C1 causes a cascade of other proteins becioming activated

Question 34

How does the alternative pathway begin?

Answer 34

With the spontaneous hydrolysis of C3

Question 35

What are pro-inflammatory cytokines?

Answer 35

IL1, IL6, TNF Secreted by sentinel cells in response to DAMPS and PAMPS Causes fever, lethargy, loss of appetite

Question 36

What kind of cells produce interferons?

Answer 36

* Produced by virally infected cells, within 24 hours of some infections

Question 37

What kind of cells can produce chemokines?

Answer 37

Sentinel Cells