Innate Immune System

Question 1

What are the three factors that determine the outcome of the host -pathogen relationship?

Answer 1

1) infectivity
2) virulence
3) host immune response

Question 2

What is infectivity

Answer 2

The ability for the microbe to attach itself within the host cell or on the host cell

Question 3

What is virulence

Answer 3

Capacity for microbe to do some damage

Question 4

What is the host immune response

Answer 4

The patients immune response - for example it is different in pregnant women , children and elderly

Question 5

Define the immune system

Answer 5

Cells and organs that contribute to defences against infectious and non infectious conditions

Question 6

What is an infectious disease

Answer 6

When the pathogen succeeds in evading /or overwhelming the hosts immune system

Question 7

What is the immune system divided into

Answer 7

1) innate immunity

2) adaptive immunity

Question 8

What are features of innate immunity

Answer 8

1) first line of defence
2) immediate protection
3) fast ( within seconds )
4) lack of specificity
5) lack of memory
6) no change in intensity

For example , the skin acts as an innate immunity barrier to pathogens and phagocytosis

Question 9

What are features of adaptive immunity

Answer 9

• long lasting protection
• second line of defence
• it is highly specific
• it is very slow ( takes a couple days )
• provides immunological memory ( memory T and B cells )
• changes in intensity

Question 10

What is the outcome e of innate immunity and adaptive immunity ?

Answer 10

Protection

Question 11

What are examples of innate immunity defences?

Answer 11

1) physical , physiological , chemical , biological barriers

Which are factors that prevent entry and limit growth of pathogens

Question 12

What are examples of physical barriers ?

Answer 12

1) skin

2) mucous membranes in the mouth , respiratory tract and GI tract , urinary tract

Question 13

What are examples of physiological barriers ?

Answer 13

1) diarrhoea - helps to expel microbe out
- vomiting : expels microbe ( eg food poisoning , hepatitis , meningitis )
- coughing ( eg in pneumonia )
- sneezing ( sinusitis )

Question 14

What are examples of chemical barriers ?

Answer 14

LOW PH in the skin (5.5)

• stomach (1-3)
• vagina (4.4- this induced lactobacillus which secretes lactic acid)

2) antimicrobial molecules eg IgA ( in tears , saliva , mucous membranes which prevents the microbe attaching to the host ). Also lysosomes which is produced in sebum , urine. Mucus which traps all the microbe. Beta defensins ( they act in a non specific manner - produced in epithelium) . And gastric acid is very acidic so microbes cannot survive here,

Question 15

What are examples of biological barriers

Answer 15

1) flora which are non-pathogen microbes
- they are found in mucus membrane areas eg skin , GI tract , vagina , mouth. Throat
- they are ABSENT in internal organs and tissues
- they compete with pathogens for attachment sites and rescources. Produce antimicrobial chemicals. They also synthesise vitamins ( K, B12, other B vitamins).
- also allow for immune maturation

Question 16

What occurs when normal flora is displaced from its normal location to sterile location ?

Answer 16

• 1) fecal-oral route ( where flora from faeces enters the mouth)
  2) fecal-perineal-urethral route ( where flora from the anus enters the vagina ) causes UTI

3 ) breaching the skin integrity eg through skin diseases , skin loss due to burns , IV lines , injecting drug users , tattooing g

4)poor dental hygiene

Question 17

What type of patients have a high risk of serious infections ?

Answer 17

1) asplenic and hyposplenic patients
2) patients with damaged or prosthetic valves
3) patients with previous infective endocarditis

Question 18

What are a few causes of when flora over grows and becomes pathogenic ?

Answer 18

1) patients with diabetes
2) patients with AIDS
3) malignant diseases
4) chemotherapy

Question 19

What are a few examples of normal flora in mucosal surfaces depleting due to antibiotics?

Answer 19

1) in vagina which causes thrush.1) taking antibiotics can kill the lactobacillus bacteria in the vagina ( this is used to help keep the vagina at a pH of 4.4 - with this occurring this disrupts the natural flora present in the vagina allowing other pathogenic yeast to grow for example Candida albicans)
2) In the intestine , taking antibiotics can allow other bacterium’s to flourish, for example clostridium difficult which causes severe colitis.( severe inflammation of the inner lining of the colon)

Question 20

Where are macrophages found ?

Answer 20

Present in all organs

Question 21

What is the role of macrophages ?

Answer 21

They ingest and destroy microbes by phagocytosis

• they present microbial antigens to T cells
• they produce cytokines /chemokines

Question 22

Where are monocytes found ?

Answer 22

In the blood (5-7%)

Question 23

What is the role of monocytes ?

Answer 23

• recruited st an infection site and differentiate into macrophages

Question 24

Where are neutrophils found ?

Answer 24

In the blood (60%)

Question 25

What increases in number during infection ?

Answer 25

Neutrophils

Question 26

What is the role of neutrophils ?

Answer 26

Recruited by chemokines to the site of infection - they ingest and destroy phonemic bacteria

Question 27

What is the role of eosinophils ?

Answer 27

Defence against multi cellular parasites ( worms )

Question 28

What is the role of basophils/mast cells?

Answer 28

- they are important in allergic responses - they are the early actors of inflammation because they contain different granules of substances eg histamine and heparin.

Question 29

What is the role of dendritic cells ?

Answer 29

Present microbial antigens to T cells ( acquired immunity)

Question 30

What are opsonins

Answer 30

Coating proteins that bind to microbial surfaces leading to enhanced attachment of phagocyte and clearance of microbes - phagocyte have the opsonin receptor

Question 31

Why is measuring the concentration of C-reactive protein important?

Answer 31

It is an inflammatory marker

Question 32

What is the most important function of the spleen ?

Answer 32

They are very important in recognising the encapsulated bacteria and clearing them from the body. - for example meningitis - encapsulated bacteria often cause invasive infections

Question 33

What are natural killer cells ?

Answer 33

They kill all abnormal host cells - this can be virus infected or malignant

Question 34

How are pathogens recognised by phagocytes ?

Answer 34

Phagocytes have pathogen recongition receptors (PRRs) which are ‘ roll like receptors’ that recognise PAMPS ( pathogen associated molecular patterns).

Question 35

Give an example of a type of pathogen recongition receptor and which type of bacteria it recognises ?

Answer 35

TLR4 recognises lipopolysaccharide (gram negative bacteria ) TLR2 recognises lipoproteins and lipopeptides ( gram negative bacteria ) TLR2 also recognises peptidoglycan gram positive bacteria TLR4 also recognises lipoteichoic acids ( gram positive bacteria )

Question 36

Give a few examples of opsonins

Answer 36

1) complement proteins (C3b and C4b) 2) antibodies : IgG and IgM. 3) acute phase proteins ( C-reactive protein & mannose-binding lectin)

Question 37

Outline the process of phagocytosis

Answer 37

1) chemotaxis and adherence of microbe to phagocyte 2) ingestion of microbe by phagocyte 3) formation of phagosome 4) fusion of phagosome with a lysosome to form a phagolysosome 5) digestion of ingested microbe by enzymes 6) formation of residual body containing indigestible material 7) discharge of waste materials

Question 38

What are the two mechanisms used by phagocytes to intracellularly kill microbes ?

Answer 38

1) oxygen dependant pathway ( respiratory burst) | 2) oxygen independent pathways

Question 39

What is the oxygen dependant pathway ?

Answer 39

- it is a mechanism where phagocytes kill microbes intracellularly - oxygen free radicals : h202, Oh*-, nitric oxide , singlet oxygen and hypohalite are used to kill microbes

Question 40

What is the oxygen independant pathway

Answer 40

Mechanism phagocytes used to kill pathogens intracellularly - use of lysosomes - lactoferrin/transferrin - hydrolytic enzymes /proteolytic enzymes

Question 41

What are examples of when phagocytosis may be reduced ?

Answer 41

1) decreased spleen function : this can be in asplenic patients or hyposplenic patients 2) decreased neutrophil number : this can be in cancer chemotherapy patients , certain drugs ( phenytoin) and leukaemia and lymphoma 3) decreased neutrophil function : chronic granulomatous disease ( no respiratory burst) and chediak -higashi syndrome ( no phagolysosomes)

Question 42

What is the complement system ?

Answer 42

Is a complex of soluble proteins present in the serum that are capable of sensing microbes and activation a chain of enzymatic chain reactions leading to the activation of various complement proteins with different anti microbial properties. The main products are : C3a-C5a, C3b-C4b , C5-C9