Immunology/Microbiology Flashcards Preview

Year 3 Semester 2 > Immunology/Microbiology > Flashcards

Flashcards in Immunology/Microbiology Deck (117):
1

Which immune cells are polymorphonucleocytes?

1. Neutrophils 2. Eosinophils 3. Basophils (granulocytes)

2

How does the tetanus vaccination work?

Stimulates antitoxin production

Does not prevent the growth of C. tetani in wounds, but protects against the toxin produced by the organism

3

Which tetanus vaccination is given to children?

DTPa

(diphtheria, tetanus, pertussis (acellular))

4

Which tetanus vaccination is given to adolescents and adults?

dTpa

Contain substantially less amounts of diphtheria toxoid and pertussis antigens than DTPa

5

When should adults receive a tetanus booster dose?

All adults aged 50 who have not had a tetanus booster in the previous 10 years

6

When is tetanus immunoglobulin (TIG) given?

If there is any doubt about the adequacy of previous tetanus immunisation in a person with a tetanus-prone wound

e.g. immunodeficiency, <3 tetanus doses or uncertain

7

Which organism causes tetanus?

Clostridium tetani

8

Which cells are phagocytes?

1. Monocytes (macrophages, dendritic cells)

2. Mast cells

3. Neutrophils

9

What is the action of C5a?

Chemotaxis

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10

What is the action of C3b?

Opsonisation (with the action of C5a)

+ helps create MAC

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11

Which complement proteins are involved in the formation of the MAC?

C5b, C6, C7, C8, C9

12

Which complement pathway requires the adaptive response for activation?

Classical

Activated by antigen-antibody complexes

13

What are anaphylatoxins?

Bind to and stimulate mast cells and basophils to degranulate

Complement peptides C3a, C4a and C5a 

 

14

Which T helper cells are involved in autoimmune reactions?

Th1 or Th17

15

Which T helper cells are involved in allergic reactions?

Th2

16

What are 3 organisms people with asplenism particularly susceptible to?

Streptococcus pneumonia

Neisseria meningitidis

Haemophilis influenzae

Klebsiella

Pseudomonas aureginosa 

17

In which area of the spleen are APCs and specialised B cells found?

Marginal zone

Between the red and white pulp - area where APCs present blood-bourne antigens

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18

In which area of the spleen are T cells found?

Periarterial lymphatic sheath of the white pulp

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19

Which immunoglobulins are measured when investigating immunodeficiency?

IgA, IgG, IgM

20

What are 3 congenital B-cell immunodeficiencies?

Brunton agammaglobulinemia (X-lined agammaglobulinemia)

Selective IgA deficiency (SIgAD)

Common variable immunodeficiency (CVID)

21

In which immunodeficiency are B cells phenotypically normal but unable to differentiate into Ig-producing cells

Common variable immunodeficiency

22

What is the most common congenital immunodeficiency?

Selective IgA deficiency

23

Which congenital B cell immunodeficiency typically has an onset at 20-35 years of age?

Common variable immunodeficiency

24

What type of infections are characteristic of complement deficiencies?

Infections from encapsulated organisms

25

What type of infections are characteristic of granulocyte deficiencies?

Skin and soft tissue infections

Catalase-positive organisms e.g. Staph aureus, Gram -ve bacilli

26

What type of infections are characteristic of T cell deficiencies?

"Benign" viruses (e.g. CMV, EBV), fungi, intracellular pathogens (e.g. mycobacteria)

27

What is the function of PRR and PAMPs?

Pattern recognition receptors (PRRs) recognise pathogen-associated molecular patterns (PAMPs) and induce cytokine release

PAMPs = products found in pathogens and not in mammals e.g. flagellin

PRR e.g. toll-like receptors

28

What is the common end point of the three complement pathways?

Splitting of C3 into C3a and C3b

29

What is the function of C3a

Enhances inflammation by stimulating histamine degranulation

30

What is a bacterial capsule?

Polysaccharide layer that lies outside the cell envelope

Prevents phagocytosis

A capsule-specific antibody is required

31

How does splenic dysfunction, asplenia or splenectomy influence the susceptibility to infection by encapsulated organisms?

1. Splenic dysfunction = decreased IgM = decreased complement activation = decreased C3b opsonization = increased susceptibility to encapsulated organisms

2. Loss of splenic macrophages

3. Reduces opsonin and properdin production

32

What is the structure of immunoglobulins?

Two heavy chains

Two light chains

The variable regions of the H and L chains are the antibody binding sites

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33

Which immunoglobulin crosses the placenta and provides passive immunity to children?

IgG

34

Which immunoglobulin is least affected by loss of immunoglobulins in the renal or gastrointestinal tract?

IgM

Largest of the immunoglobulins

35

Which is the most potent cytokine?

IL-6

36

How do glucocorticoids suppress the immune system?

Decreased transcription of pro-inflammatory genes 

→ Inhibits neutrophil binding to the vessel wall (less emigration to tissues)

→ Inhibits leukocyte activity

Neutrophil infections - staph, strep, candida

Lymphocyte infections - herpes, mycobacteria, salmonella

37

Delayed loss of the umbilical cord is associated with which immunodeficiency?

Leukocyte adhesion deficiency

Poor migration of immune cells from the vessel wall, particularly neutrophils

38

What is defective in chronic granulomatous disease?

Deficiency of superoxide production by polymorphoneutrophils and macrophages → ability to ingest but not kill microorganisms → granuloma formation

39

What is the mechanism of natalizumab?

Stops leukocytes from adhering to vessel walls

Cannot reach tissues to cause inflammation

40

What is the mechanism of fingolimod?

Blocks sphingosine-1-phosphate receptor

Lymphocytes accumulate in lymph nodes → not able to travel to tissues

 

41

When is infection a contraindication to vaccination?

Temperature > 38.5 degrees

Minor coughs and colds are ok

42

Which test is used to assess the complement system?

CH100/50

43

How do immunomodulators affect infection risk?

They do not increase the risk of infection as they are not immunosuppressive

44

What is the mechanism of azathioprine?

Purine antimetabolite

Impairs lymphocyte proliferation, cellular immunity and antibody responses

45

What feature is unique to splenic macrophages?

Can detect and capture encapsulated bacteria

Normal macrophages detect proteins, but the polysaccharide wall is a sugar

46

What is a unique feature of B cells in the splenic marginal zone?

Can initiate T cell-independent immune reactions

47

What occurs in the cortex of lymph nodes?

B cell proliferation occurs in germinal centres

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48

What lies in the paracortex of lymph nodes?

T cells

49

What is the role of dendritic cells in lymph nodes?

Dendritic cells are activated → enter lymph node → present antigen to T cells → T cells activate B cells → antibody production

50

Why are patients with diabetes immunocompromised?

Neutrophil dysfunction → bacterial and fungal infections

Poor peripheral circulation → ulceration + poor delivery of neutrophils 

51

Which immunoglobulin(s) are affected by asplenism?

IgM

52

Which immunoglobulin is involved in type III hypersensitivity reactions?

IgG

53

Why do type I hypersensitivity reactions occur so rapidly?

IgE coats mast cells and basophils with initial contact with the antigen

Antigen readily binds to IgE with subsequent exposure and causes degranulation

 

54

Which immunoglobulin(s) are involved in type II hypersensitivity reactions?

IgM and IgG

Bind to antigens → complement activation → cellular lysis and phagocytosis

55

What is tryptase?

Specific marker of mast cell activation

If elevated → increased risk of anaphylaxis

56

What is the mechanism of montelukast?

Leukotriene receptor antagonist

May be used for long-term asthma control

57

What is the mechanism of complement-dependent type II hypersensitivity reactions?

1. IgG and IgM bind to antigens

2. Complement activation (classical)

3. Cellular lysis or phagocytosis

E.g. autoimmune haemolytic anaemia, pemphigus vulgaris, drug reactions

58

What is the mechanism of antibody-dependent cell-mediated cytotoxic type II hypersensitivity reactions?

Ab + Ag → activation of NK cells → cell lysis without phagocytosis

Destruction of targets too large to be phagocytosed e.g. parasites, tumour cells, graft rejection

59

What is the mechanism of antibody-mediated cellular dysfunction type II hypersensitivity reactions?

Antibodies directed against cell surface receptors → impaired or dysregulated cell dysfunction

E.g. MG, Goodpasture's, pernicious anaemia, acute rheumatic fever

60

What are the three potential mechanisms of type II hypersensitivity reactions?

Complement-dependent

Antibody-dependent cell-mediated cytotoxicity

Antibody-mediated cellular dysfunction

61

What type of hypersensitivity is myasthenia gravis?

Type II (antibody-mediated cellular dysfunction)

Antibodies bind to post-synaptic ACh receptors, competing with ACh

62

What type of hypersensitivity reaction is Goodpasture's syndrome?

Type II (antibody-mediated cellular dysfunction)

Antibodies against type IV collagen (in basement membrane of glomerulus → glomerulonephritis + acute renal failure)

Can also affect alveoli

63

What type of hypersensitivity reaction is pernicious anaemia?

Type II (antibody-mediated cellular dysfunction)

Antibodies against intrinsic factor and/or parietal cells

64

What type of hypersensitivity reaction is autoimmune haemolytic anaemia and acute haemolytic transfusion reaction?

Type II (complement-dependent)

65

What type of hypersensitivity reaction is pemphigus vulgaris?

Type II (complement-dependent)

66

What type of hypersensitivity reaction is rheumatic fever?

Type II

Antibodies against streptococcal M protein

67

What type of hypersensitivity reaction is lupus?

III

68

What are the two forms of type IV hypersensitivity?

1. Delayed-type

2. T-cell mediated

69

What is the pathophysiology of delayed-type IV sensitivity?

Antigen exposure → CD4+ and MHC-II activation → CD4+ differentiation to TH1 → inflammatory reaction

E.g. TB skin test, contact dermatitis, granulomatous inflammation

70

What is the pathophysiology of cell-mediated cytotoxic IV sensitivity?

Sensitisation of CD8+ cells

Graft rejection, viruses, tumour immunity, intracellular pathogens e.g. TB

71

What type of hypersensitivity reaction is GBS?

Type IV

72

What type of hypersensitivity reaction is T1DM?

Type IV

73

What is the role of glucocorticoids in anaphylaxis?

Prevention of late phase reaction (limited evidence, but no harm)

74

What are 3 mechanisms of peripheral T cell tolerance?

1. Anergy (no second signal)

2. Block in activation (suppression)

3. Deletion (apoptosis)

75

What types of vaccination are given to asplenic patients?

Conjugate or recombinant

Both contain have a protein component which stimulates T cell proliferation

76

Which type of bones contain red bone marrow?

Flat bones e.g. pelvis

Long bones

77

What is positive selection?

T cells that generate a functional receptor and can bind with self MHC molecules proliferate

78

What is negative selection?

Removes thymocytes that bind to MHC self-peptides

79

What is the most common cause of angioedema from direct mast-cell activation (non-IgE mediated)?

NSAIDs

80

What is the risk of HIV transmission in MSM?

0.5% for a receptive partner

81

What is the risk of HIV transmission in male to female intercourse?

0.1% for female partner

0.05% for male partner

HIV concentration is higher in male ejaculate than in vaginal secretions

82

Which HIV proteins help the virus attach to CD4 receptors?

gp120 and gp41 (envelope proteins)

83

Which protein helps viruses convert viral RNA to DNA?

Reverse transcriptase

84

Which protein is required to insert viral genes into the host genome?

Integrase

85

What is the definition of a retrovirus?

Genome is stored in RNA rather than DNA

86

Which immune cells have CD4 receptors?

T lymphocytes

Macrophages

Monocytes

Dendritic cells

87

Which two things must be present for HIV virus to enter a cell?

CD4 receptor

Coreceptor (CCR4 in T cells and CCR5 in all other CD4 cells)

88

A mutation in what is associated with HIV immunity?

Homozygous CCR5 mutation = immunity

Heterozygous CCR5 mutation = slower disease progression due to impaired viral spread

89

What is acute retroviral syndrome?

Acute HIV syndrome

Fever, fatigue, lymphadenopathy, myalgia/arthralgia, headache, rash, GI symptoms, sore throat, ulcerations, painful swallowing

Similar to mono (rashes and diarrhoea more prevalent)

90

What is HIV wasting syndrome?

Unintentional weight loss of >10%, fever, fatigue, diarrhoea

91

What is kaposi sarcoma?

Tumour of the skin and mucosa caused by herpes virus 8

Most common HIV-associated tumour

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92

What is the most common opportunistic bacterial infection in AIDS patients?

Mycobacterium avium complex (MAC infection)

 

93

What is progressive multifocal leukoencephalopathy?

Reactivation of JC virus → infects oligodendrocytes → aggressive replication within brain tissue → destruction of infected oligodendrocytes + demyelination

Focal symptoms, seizures, impaired vigilance, cognitive disorders, behavioural changes

94

What is the most common cause of death in AIDS patients?

Pneumocystitis pneumonia

Caused by pneumocystitis jiroveci (fungus)

Occurs almost exclusively in immunocompromised patients

95

What is the HIV window period?

Time between infection and detectability of HIV antibodies

2-6 weeks

96

List 10 AIDS-defining conditions

1. HIV wasting syndrome

2. Kaposi sarcoma

3. Cervical cancer

4. Lymphoma

5. TB reactivation

6. Coccidioidomycosis

7. Cryptosporidiosis

8. HIV-related encephalopathy

9. PML

10. Pneumocystitis pneumonia

11. Isosporiasis

12. Histoplasmosis

13. Cerebral toxoplasmosis

14. Candidiasis

15. Herpes simplex infections

16. CMV infection

17. MAC infection

18. HIV retinopathy

19. Bacillary angiomatosis

20. VZ/CMV retinitis

21. Herpes simplex keratitis

22. Cerebral abscess

23. Primary CNS lymphoma

97

A CD4 count less than what is definitive of AIDS irrespective of symptoms?

<200 cells/uL

98

Which virus causes Kaposi sarcoma?

Herpes virus 8

99

What is the first-line investigation for diagnosing HIV?

HIV Ag/Ab

Detects HIV antigen (p24) and anti-HIV antibodies

Near 100% sensitivity

100

Which test is used following a positive HIV Ag/Ab result?

HIV-1/HIV-2 antibody differentiation immunoassay

101

Which investigations should be ordered on initial evaluation of suspected HIV?

1. HIV serology

2. CD4 count

3. HIV viral load

4. Resistance testing

5. HLA-B*5701 testing

6. Hepatitis B/C serology

7. FBC + electrolytes

8. LFTs

9. Lipids

10. HbA1c

11. Urinalysis

12. Pregnancy test

13. Screening for other STIs

 

102

Which allele should be tested upon initiation of abacavir?

HLA-B*5701

Hypersensitivity

103

What are 4 drug classes used in the treatment of HIV?

1. Nucleoside reverse transcriptase inhibitors

2. Non-nucleoside reverse transcriptase inhibitors

3. Protease inhibitors

4. Integrase inhibitors

5. Fusion inhibitor

6. Nucleoside analogues

7. CCR5-antagonist

104

What are two examples of HIV antiretroviral regimens?

3 NRTI

OR

2 NRTI + 1 NNRTI / protease inhibitor / integrase inhibitor

105

Name 3 reverse transcriptase inhibitors

1. Zidovudine

2. Lamivudine

3. Emtricitabine

4. Abacavir

5. Stavudine

5. Didanosine

mostly end in "-ine"

106

Name 2 non-nucleoside reverse transcriptase inhibitors

1. Nevirapine

2. Efavirenz

107

Name two protease inhibitors

Indinavir

Ritonavir

Nelfinavir

Lopinavir

end in "-avir"

108

Name two integrase inhibitors

 

Raltegravir

Dolutegravir

end in "-gravir"

109

What are 3 adverse effects of nucleoside reverse transcriptase inhibitors?

1. Bone marrow suppression (neutropenia, anaemia)

2. Mitochondrial toxicity (lactic acidosis, myopathy, neuropathy)

3. HIV-associated lipodystrophy

4. Hypersensitivity (abacavir)

5. Pancreatitis (didanosine/stavudine)

 

110

----- is a CNS protozoal infection that presents with brain abscesses in HIV patients, that are seen as ring-enhancing brain lesions on CT/MRI

Toxoplasmosis

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111

Which protozoa causes toxoplasmosis?

Toxoplasma gondii

112

How is toxoplasmosis transmitted?

The oocytes are excreted in the faeces of cats and are orally ingested by other mammals such as humans, hoofed animals, and birds. Primary modes of transmission therefore include:

Cat feces

Raw or insufficiently cooked meat

Unpasteurized milk (especially goat milk)

113

Which opportunistic fungus causes pneumonia in HIV patients?

Pneumocystic jirovecii

114

Which type of vaccination should not be given to immunocompromised patients?

Live attenuated

115

------ is a dermatological infection caused by EBV in HIV patients that commonly presents on the lateral tongue

Hairy leukoplakia

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116

------ is a protozoa that causes GI infection in HIV patients that presents with chronic, watery diarrhoea

Cryptosporidium spp

Acid fast cysts are seen in the stool

 

117

------- is an opportunistic fungus that causes meningitis in HIV patients

Cryptococcus neoformans