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Infection > Innate Immune System > Flashcards

Innate Immune System Flashcards

1
Q

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

A

1) infectivity
2) virulence
3) host immune response

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2
Q

What is infectivity

A

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

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3
Q

What is virulence

A

Capacity for microbe to do some damage

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4
Q

What is the host immune response

A

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

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5
Q

Define the immune system

A

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

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6
Q

What is an infectious disease

A

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

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7
Q

What is the immune system divided into

A

1) innate immunity

2) adaptive immunity

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8
Q

What are features of innate immunity

A

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

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9
Q

What are features of adaptive immunity

A
  • 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
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10
Q

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

A

Protection

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11
Q

What are examples of innate immunity defences?

A

1) physical , physiological , chemical , biological barriers

Which are factors that prevent entry and limit growth of pathogens

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12
Q

What are examples of physical barriers ?

A

1) skin

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

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13
Q

What are examples of physiological barriers ?

A

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

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14
Q

What are examples of chemical barriers ?

A

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,

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15
Q

What are examples of biological barriers

A

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

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16
Q

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

A
  • 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

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17
Q

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

A

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

18
Q

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

A

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

19
Q

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

A

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)

20
Q

Where are macrophages found ?

A

Present in all organs

21
Q

What is the role of macrophages ?

A

They ingest and destroy microbes by phagocytosis

  • they present microbial antigens to T cells
  • they produce cytokines /chemokines
22
Q

Where are monocytes found ?

A

In the blood (5-7%)

23
Q

What is the role of monocytes ?

A
  • recruited st an infection site and differentiate into macrophages
24
Q

Where are neutrophils found ?

A

In the blood (60%)

25
Q

What increases in number during infection ?

A

Neutrophils

26
Q

What is the role of neutrophils ?

A

Recruited by chemokines to the site of infection

  • they ingest and destroy phonemic bacteria
27
Q

What is the role of eosinophils ?

A

Defence against multi cellular parasites ( worms )

28
Q

What is the role of basophils/mast cells?

A
  • they are important in allergic responses
  • they are the early actors of inflammation because they contain different granules of substances eg histamine and heparin.
29
Q

What is the role of dendritic cells ?

A

Present microbial antigens to T cells ( acquired immunity)

30
Q

What are opsonins

A

Coating proteins that bind to microbial surfaces leading to enhanced attachment of phagocyte and clearance of microbes

  • phagocyte have the opsonin receptor
31
Q

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

A

It is an inflammatory marker

32
Q

What is the most important function of the spleen ?

A

They are very important in recognising the encapsulated bacteria and clearing them from the body.

  • for example meningitis
  • encapsulated bacteria often cause invasive infections
33
Q

What are natural killer cells ?

A

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

34
Q

How are pathogens recognised by phagocytes ?

A

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

35
Q

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

A

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 )

36
Q

Give a few examples of opsonins

A

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

37
Q

Outline the process of phagocytosis

A

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

38
Q

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

A

1) oxygen dependant pathway ( respiratory burst)

2) oxygen independent pathways

39
Q

What is the oxygen dependant pathway ?

A
  • 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
40
Q

What is the oxygen independant pathway

A

Mechanism phagocytes used to kill pathogens intracellularly

  • use of lysosomes
  • lactoferrin/transferrin
  • hydrolytic enzymes /proteolytic enzymes
41
Q

What are examples of when phagocytosis may be reduced ?

A

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)

42
Q

What is the complement system ?

A

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

Infection (24 decks)

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