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PPE - Rhianna > Infection and Immunity > Flashcards

Infection and Immunity Flashcards

1
Q

Give some physical adaptations of the innate immune system.

A

Skin, mucous membranes, cilia

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2
Q

Give some physiological adaptations of the innate immune system.

A

Vomiting, diarrhoea, coughing, sneezing

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3
Q

Give some chemical adaptations of the innate immune system.

A

Low ph in stomach and vagina
Complement
Cytokines

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4
Q

Give some biological adaptations of the innate immune system.

A

Normal flora in the gut, vagina, nasopharynx etc compete for space and resources so keep pathogens at bay.

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5
Q

What are the three main functions of complement?

A

Opsonisation
Recruitment of phagocytes
Killing microbes directly

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6
Q

Where is complement produced?

A

Spleen

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7
Q

What are the three main functions of cytokines?

A

Increases complement
Recruit phagocytes
Inflammation - vasodilation, increase permeability and coagulation cascade, increase temperature.

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8
Q

Where are cytokines produced?

A

Macrophages.

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9
Q

How does the innate immune system recognise a microbe? 2 ways.

A
  1. Pathogen recognition receptors (PRRs) find pathogen associated molecular patterns (PAMPs)
  2. Microbe triggers release of opsonins which coat the microbe and the phagocytes follow the opsonins and recognise them with opsonin receptors.
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10
Q

What are the functions of macrophages?

A

Phagocytosis
Release cytokines for inflammation and release of complement
Present antigens to T cells

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11
Q

Describe the process of phagocytosis.

A

Engulfment into phagosome
Lysosome joins to become phagolysosome
Digestion of microbe by 1. Free radicals 2. Lysozyme
Release of digested products.

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12
Q

What is the purpose of opsonisation? In which case is it essential?

A

Aids the recognition of microbes.

Essential if bacteria is encapsulated (eg neisseria meningitidis) because no PAMPs can be recognised.

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13
Q

Why are asplenic patients at an increased risk of overwhelming infection?

A

Spleen releases complement including opsonins.
Therefore
Decrease in ability to recognise microbes (particularly encapsulated eg neisseria meningitidis because no visible pamp without opsonin) and decrease in ability to recruit phagocytes.

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14
Q

Which patients have a decreased neutrophil count? Why does this matter?

A

Chemotherapy
Phenytoin
Chronic granulomatous disease

Decreased phagocytosis and increased risk of overwhelming infection.

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15
Q

What is the function of normal flora?

A

Keep pathogens (and each other) from causing disease by competitive antagonism.

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16
Q

How do antibiotics increase the risk of some infections? Which infections are they?

A

Disrupt the balance of normal flora and allow some to over grow.

Eg thrush and clostridium difficile (esp with cephtriaxone - cephalosporin)

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17
Q

What is SIRs? How does it present?

A

Systemic inflammatory response

High temperature, high heart rate, high resp rate, high wbcs, (low bp, acute kidney injury)

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18
Q

What is acute sepsis? How does it present?

A

SIRs (systemic inflammatory response) plus an infection

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19
Q

What is the pathogenesis of acute sepsis?

A

Bacteria growth overcomes phagocytosis. Immune response increases, increase in complement and cytokines. Response becomes systemic.

Cytokines lower bp by vasodilation and increased permeability
Baroreceptors compensate by increasing sympathetic so increase hr. Can’t vasoconstrict because too many cytokines.

Cytokines trigger coagulation cascade, leading to micro vascular necrosis and acute kidney injury.

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20
Q

What are the “sepsis six” actions for sepsis?

A
  1. O2
  2. IV fluids
  3. Antibiotics
  4. Culture
  5. Serum lactate
  6. Urine output
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21
Q

What are the characteristics of the innate immune system?

A

Immediate, fast, non specific, no memory

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22
Q

What is an antigen?

A

A peptide marker of a cell that is recognised by an antigen presenting cell

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23
Q

Give two examples of antigen presenting cells.

A

Macrophages

Dendrites

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24
Q

Which particles in the antigen presenting cell recognise the antigen?

A

MHC particles

MHC 1 - intracellular
MHC 2 - extra cellular

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25
Q

How does the immune system differentiate between bacteria and viruses?

A

Extra cellular and intracellular recognition of antigens. Viruses will be intracellular.

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26
Q

What are the roles of the two types of T cell?

A

Cd4 helper - activate plasma B cells to switch to igg production, activate phagocytosis, activate mast cells.

Cd8 - cytotoxic

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27
Q

What are the roles of the two types of B cell?

A

Plasma - secrete antibodies

Memory - increase the rate of antibody response next time

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28
Q

Do MHC molecules respond to self antigens? Why?

A

Yes they are non specific to maximise recognition of new microbes

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29
Q

Do T cells respond to self antigens? Why?

A

No. Naive T cells are activated by their first antigen and go on to only respond to that antigen. Any naive T cell that is activated by a self antigen will die so no T cells respond to self antigens.

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30
Q

How does the adaptive immune system confer memory and specificity?

A
  1. B memory cells
  2. Active T cells only respond to one antigen. They are able to respond more quickly if already active and not naive.
  3. Specific antibodies
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31
Q

What are the functions of IgM, IgG and IgE?

A

IgM - normally circulating, general complement activation
IgG - secreted by plasma B cells in response to T cell activation. Has specific toxin neutralisation as well as complement activation.
IgE - activates mast cells to respond to allergens

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32
Q

What are the two types of staphylococcus?

A

Staphylococcus Aureus (coagulase positive)

Coagulase negative

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33
Q

What are the main pathogens responsible for hospital /community acquired pneumonia? How would you treat each?

A

Hospital acquired - staphylococcus aureus (high chance of resistance so at least co-amoxiclav or vancomycin) or haemophilus influenzae

Community acquired - streptococcus pneumoniae (penicillin)

34
Q

What diseases are caused by staph aureus?

A

Cellulitis
Hospital acquired pneumonia
MRSA

35
Q

What diseases are caused by coagulase negative staphylococcus?

A

Prosthetic surface infections (central line, IV, intubated, prosthetic joints and valves)
Endocarditis on a prosthetic valve
UTI from catheters

36
Q

What are the main pathogens responsible for natural valve/prosthetic valve acquired endocarditis?

A

Natural valve - streptococcus viridans

Prosthetic valve - coagulase negative staphylococcus

37
Q

In which two ways can streptococcus be classified?

A

By group - A is highly virulent. B is only infective for neonates and immunocompromised

By haemolysis - alpha is partial. Beta is complete. Gamma is none.

38
Q

What is the classification of streptococcus pneumoniae? What diseases des it cause?

A

Group A alpha haemolytic.
Community acquired pneumonia
Meningitis

39
Q

What is the classification of streptococcus pyogenes? What diseases des it cause?

A

Group A, alpha haemolytic
Strep throat - pharyngitis
Necrotising fasciitis

40
Q

What is a biofilm? How does it help the bacteria survive?

A

Colony of bacteria secreting mucopolysaccharides - often on a prosthetic surface eg valve or joint.

Increases adherence
Reduces antibiotic penetration

41
Q

What is a danger of biofilm formation?

A

Embolism to small vessels

Especially form brain abcesses

42
Q

What is a hypersensitivity reaction?

A

Antigen specific immune response that is either inappropriate or excessive

43
Q

Which immune cell phenotype is more prone to hypersensitivity/allergy?

A

TH2 phenotype of CD4 t helper cell is more prone

TH1 is protective

44
Q

What happens on first exposure to an allergen?

A

CD4 T helper cell tells the B cells to switch their antibody production from IgM to IgE.
IgE attaches to mast cells and primes them.

No symptoms.

45
Q

What happens on second exposure to an allergen?

A

Antigen of allergen crosslinks between the IgE molecules on the primed mast cell.

Mast cell releases histamine and this stimulates leukotrienes and prostaglandins

46
Q

What 3 chemical mediators are associated with allergic reaction?

A

Histamine
Leukotrienes
Prostaglandins

47
Q

What 3 happens to the blood vessels and lungs in response to allergic chemical mediators?

A

Vasodilation
Increased permeability of vessels
Bronchoconstriction

48
Q

What are the 4 symptoms of allergic reaction?

A

Hypotension
Urticaria - wheal and flare rash
Angio oedema
Dyspnoea

49
Q

What is the difference in pathophysiology between urticaria and angio oedema?

A

Urticaria - vasodilation and increased permeability in the epidermis

Angio oedema - vasodilation and increased permeability in the deep dermis

50
Q

What serum test can be used to identify an allergic reaction?

A

Serum mast cell tryptase

51
Q

In a skin prick allergy test, what would mark a positive response?

A

Wheal and flare

Compared with control of histamine which should be positive and saline which should be negative

52
Q

How does a bacteria confer resistance to antibiotics?

A
  1. Vertical
    Rapid multiplication leads to mutants being produced.
    If a mutant has a resistant feature, this will survive and replicate when an antibiotic kills the other bacteria.
    This mutant strain will be resistant to that anti biotic.
  2. Horizontal
    Transfer of mutant material via transposons and plasmids
53
Q

How can we minimise antibiotic resistance?

A
  1. Minimise prescription of antibiotics - minimise their exposure
  2. During treatment of risky bacteria such as TB give triple drug therapy so that a mutant resistant to one antibiotic should be mopped up by one of the others
54
Q

Give 10 notifiable diseases. Who should you report them to?

A

Local health protection team

TB
Measles
Mumps
Rubella
Polio
Typhoid fever
Malaria
Rabies
Tetanus
Infectious hepatitis
55
Q

Give an infection that may be transmitted via a common water source?

A

Legionella pneumophilia

56
Q

Give an infection that might be transmitted via the feco oral route.

A

E. coli

Polio

57
Q

Give an infection which might be transmitted via an animal.

A 
Rabies
MERs coV (via camels)
58
Q

Give some infections that are only transmitted from person to person

A

Sti - neisseria gonorrhoea, chlamydia trachomatis

Virus - Influenza, norovirus

59
Q

Give an example of some infections transmitted via a vector.

A

Malaria

MRSA via hospital equipment

60
Q

What is the difference between an epidemic and a pandemic?

A

Epidemic - rate greater than the endemic background rate

Pandemic - rate much greater than endemic, that has spread across many regions and countries

61
Q

What is the basic reproduction number of an infection (R0)? What is significant about r01?

A

The average number of cases generated by a single case of infection, in an otherwise healthy population.

If it is greater than 1 - increase in cases
Less than 1 - decrease in cases

62
Q

What factors can make a pathogen prone to epidemic?

A

New antigens appear new to the immune system eg H1N1 to H5N1
New virulence factors eg
Antibacterial resistance

63
Q

What factors can make a host susceptible to infection?

A

Immunosuppression

Age - Young and old

64
Q

Give some virulence factors which aid colonisation of the host.

A

Invasins
Adhesins
Anti phagocytise factors (eg TB cell wall)

65
Q

Give some virulence factors which aid damage to the host.

A

Exotoxins
Endotoxins
Proteases
Haemolysins

66
Q

Which types of bacteria tend to express lots of virulence factors?

A

Gram negative

67
Q

Give 3 examples of good infection control practice within hospital

A

Give disinfectant body wash to all patients - reduce MRSA
Negative pressure side room
Handwashing

68
Q

Give an intervention acting on the pathogen/vector to decrease infection rates.

A

Decrease Mosquitos - malaria

Disinfectants

69
Q

Give an intervention acting on the host to decrease infection rates.

A

Improve herd immunity via vaccination - eg smallpox

70
Q

What is meant by herd immunity?

A

Minimise the ability for a pathogen to spread by vaccinating enough people.

If Basic reproductive number is low, need to vaccinated a much lower number to confer herd immunity.

71
Q

What is CRP?

A

An acute phase protein produced by the liver to help opsonisation.
It is a non specific marker of inflammation.

72
Q

What is the pathogenesis of C. difficile?

A

Enterotoxin causes secretion of fluid in the gut

73
Q

What causes vasodilation during sepsis?

A

Lipopolysaccaride exotoxins or endotoxins

74
Q

Why are patients with diabetes more prone to infections?

A
  1. Glycemia and
  2. acidaemia impair wbcs and ideal environment for bacterial growth.
  3. Micro and macro vascular damage - poor perfusion for immune response
  4. Neuropathy means poor sensation and injury is not noticed
75
Q

Which types of infection are diabetics prone to?

A
  1. Cellulitis - staph aureus
  2. Otitis externa - pseudomonas aeruginosa
  3. Thrush - Candida albicans
  4. UTI - E. coli as well as specifically pseudomonas aeruginosa (only occurs in people with neuropathic bladder control.)
76
Q

Why are people with cystic fibrosis more prone to infection?

A
  1. Damage to ciliary escalator
  2. Mucosal stasis
  3. Long term steroids
  4. Antibiotic use disrupting the microbiome
77
Q

What types of infections are people with cystic fibrosis prone to?

A
  1. General serious lung infections - haemophilus influenza, strep pneumoniae, staph aureus
  2. Specific serious lung infections - pseudomonas aeruginosa, burkholderia cepacia.

Also Candida albicans and mycobacteria due to use of antibiotics.

78
Q

What are the four characteristics of an immunocompromised host?

A

Infections that are

Severe
Persistent
Unusual
Recurrent

79
Q

Give 3 examples of primary immunodeficiencies and the types of infection they would cause.

A
  1. T cell deficiency (eg DiGeorge syndrome causing a lack of thymus)
    Leads to viral and fungal infection
  2. B cell deficiency (eg inability to switch to IgA or IgG) leads to bacterial and fungal infection
  3. Phagocyte deficiency (eg chronic granulomatous disease) leads to bacterial and fungal infections.
80
Q

Give 6 examples of secondary immunodeficiencies.

A

Loss of immunoglobulin

  1. Burns
  2. Nephrotic syndrome

Decreased production

  1. Liver disease
  2. Asplenic
  3. HIV
  4. Drug induced neutropenia (chemotherapy, clozapine, steroids)
81
Q

Give 3 functions of the spleen.

A
  1. Identification of encapsulated bacteria (eg neisseria meningitidis, strep pneumoniae)
  2. Produce immunoglobulins (igG normally and IgM in acute phase)
  3. Contains macrophages for phagocytosis.
82
Q

Give 2 bacteria that cause atypical pneumonia

A

Legionella pneumophilia

Mycoplasma pneumoniae

PPE - Rhianna (7 decks)

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