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Clinical Pathology (RIP) > T4 - L4 immunodeficiency > Flashcards

T4 - L4 immunodeficiency Flashcards

1
Q

why does the immune system need to carry out self-regulation?

A

important to minimise host damage

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2
Q

features of the innate immune system?

A
  • general/recognises broad classes e.g. bacteria
  • rapid onset
  • response doesn’t change with repeated exposure
  • no memory (same response each time)
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3
Q

features of the adaptive immune system?

A
  • antigen specific
  • slower response
  • more potent response
  • memory
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4
Q

what is immunodeficiency?

A

the immune system is not effective enough to protect the body against infection

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5
Q

what is primary immunodeficiency?

A

Inherent defect within the immune system- usually genetic.

rare

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6
Q

what is secondary immunodeficiency?

A

Immune system affected due to external causes

[e.g. burns, massive cut]

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7
Q

what are causes of secondary immunodeficiency?

A
  • break down of physical barriers
  • protein loss
  • malignancy
  • drugs
  • infection
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8
Q

how can protein loss cause secondary immunodeficiency?

A

d unable to produce the Ab needed

for the infection

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9
Q

how can lymphoma cause secondary immunodeficiency?

A
  • cancer of lymphocyte s
  • expands in the
    bone marrow, limiting the space for other immune system parts to develop
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10
Q

how can steroids cause secondary immunodeficiency?

A
  • Steroids work by supressing the immune system

- Recurrent courses of steroid can cause immunodeficiency

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11
Q

how can DMARDS cause secondary immunodeficiency?

A

(Disease-modifying anti-rheumatic drugs)

  • Work by suppressing the immune system
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12
Q

how can Rituximab cause secondary immunodeficiency?

A
  • Rituximab works against B-cells
  • Clearing B-cells causes no antibody production
  • Excessive use could cause immunodeficiency
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13
Q

how can Myelosuppressive cause secondary immunodeficiency?

A

Myelosuppressive works by suppressing the bone marrow where the
immune system is generated

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14
Q

which drugs can cause secondary immunodeficiency?

A

Steroids, DMARDS, Rituximab, anti-convultants, myelosuppressive

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15
Q

Phagocytes including neutrophils and macrophages are capable of engulfing and absorbing bacteria. Which phagocyte out of the two is short-lived?

A

[Neutrophils are short lived (hours)]

[Macrophages are long lived (days, weeks)]

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16
Q

what do lysosomes produce during phagocytosis in order to kill pathogens?

A

hypochlorous acid (i.e. bleach)

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17
Q

how do pathogens know whether an antigen is self or foreign?

A 
Pathogen recognition receptors (PRRs) - recognise conserved pathogen associated
molecular patterns (PAMPs) which are unique to each pathogen
  • phagocytes have PRRs for PAMPs
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18
Q 
what is pathogen associated
molecular patterns (PAMPs)?
A

[PAMPs are things found in most or a group of bacteria, which differentiate them
from the human’s cells]

  • unique to each pathogen
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19
Q

give an examples of a common PAMPs?

A

Lipopolysaccharide

flagellin

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20
Q

what PRR recognises the PAMP Lipopolysaccharide?

A

Toll Like Receptor 4 (TLR 4)

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21
Q

what PRR recognises the PAMP flagellin?

A

TLR5

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22
Q

what PRR recognises the viral RNA?

A

TLR3

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23
Q

what happens when a phagocyte detects a pathogen via a PRR?

A

Cascade of events → production of inflammatory
cytokines

MyD88 and IRAK4 are involved in this cascade

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24
Q

Once a phagocyte has recognised a PAMP via a PRR, what two proteins are involved in the following cascade?

A

MyD88 and IRAK4

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25
Q

what happens in IRAK4 deficiency?

A

phagocytes can recognise the pathogen but cannot cause an inflammatory response

26
Q

what is the clinical presentation of IRAK4 deficiency?

A
  • Recurrent bacterial infection
  • Poor inflammatory response
  • Susceptibility to infection decreases with age
27
Q

how would you treat IRAK4 deficiency?

A

prophylactic antibiotics, iv immunoglobulin if severe

28
Q

what is a phagolysosome?

A

when a bug has been ingested by a phagocyte and is attached to a lysosome

29
Q

what is a NADPH complex?

A

complex of proteins incl gp91phox (coded by the X chromosome) found on the surface of lysosomes

30
Q

how does the NADPH complex help phagocytosis?

A
  • releases an electron within the lysosome
  • binds to 02 forming superoxide
  • superoxide gives rise to hypocholorus acid - which kills pathogen
31
Q

how is hpocholorus acid formed?

A
  • NADPH complex
  • releases an electron within the lysosome
  • binds to 02 forming superoxide
  • superoxide gives rise to hypocholorus acid
32
Q

what is a granuloma?

A

collection of macrophages

33
Q

what causes chronic granulomatous disease?

A
  • NADPH complex dysfunction
  • Mutation in gp91phox, which is encoded by
    X-chromosomes
  • X-linked condition
34
Q

what happens in chronic granulomatous disease?

A
  • NADPH complex dysfunction
  • Can ingest the bug but cannot destroy it
  • But still attracting neutrophils and macrophages in the area - Causing granuloma
35
Q

what is the treatment for chronic granulomatos disease?

A

haemopoeitic stem cell transplant, antibiotics

NB: [Bone marrow transplant is the standard treatment for Chronic
Granulomatous Disease, replacing the entire immune system]

36
Q

how do you diagnose Chronic Granulomatos Disease?

A

Measure Dihydrorhodamine reduction (gain of electron)

OR

Nitro blue tetrazolium dye reduction – healthy neutrophils should go [from clear to] purple

  • [Healthy individuals show change in neutrophil colour to purple]
  • [Patients with CGD show no change in neutrophil colour]
  • [Carriers of CGD show change in some of the neutrophils to purple]
37
Q

what 3 things do complement proteins do?

A
  • cell lysis (kill invading bacterium)
  • control of inflammation
  • stimulate phagocytosis
38
Q

what 3 pathways stimulates the complement cascade?

A

classical pathway

alternative pathway

mannose-binding lectin (MBL) pathway

39
Q

what is the end product of the complement cascade?

A

Membrane Attack Complex (MAC)

  • causes cell lysis and rupture (death)
40
Q

how can complement deficiency lead to autoimmunity?

A
  • Complement helps with clearing dead tissues

- If a person cannot clear them, they become prone to autoimmunity

41
Q

what conditions can a C2, C4 complement deficiency lead to?

A

SLE

infections

myositis

42
Q

what is myositis?

A

autoimmunity against muscles

43
Q

what condition can a C5-C9 complement deficiency lead to?

A

bacterial meningitis

C5-C9 (form membrane attack complex)

  • usual treatment: prophylactic penicillin B
44
Q

repeated episodes of bacterial meningitis would indicate what type of autoimmune disease?

A

C5-C9 complement deficiency

45
Q

how does an antibody inactivate an antigen when it binds?

A
  • neutralisation
  • agglutination of microbes
  • precipitation of dissolved antigen

NB: all activate complement cascade and leads to cell lysis

46
Q

what is meant by neutralisation?

A

antibody blocks viral binding sites/coats bacteria

47
Q

what is meant by agglutination?

A

antibodies stick microbes together

48
Q

what is meant by precipitation of dissolved antigen?

A

stick antigens together

49
Q

X linked agammaglobulinaemia is a genetic defect in what?

A

Bruton’s Tryrosine kinase

  • Needed for B cell signalling and B cell maturation - B cell maturation not completed
  • antibodies can not be produced
50
Q

what conditions. can arise due to B cell defects?

A
  • CVID
  • IgA deficiency
  • X Linked hyper IgM syndrome
  • Transient hypogammaglobulinaemia of infancy
51
Q

what happens if there are defects in B cells?

A
  • loss of antibody secretion
  • Usually leads to recurrent bacterial infection with pyogenic organisms
  • Treat with [prophylactic] antibiotics [e.g. azithromycin] then i.v IgG for life.
52
Q

conditions that arise due to B cell defects are mostly very serious - however which one is asymptomatic?

A

IgA deficiency

  • [Common]
  • [Mostly asymptomatic but some people develop recurrent infections and become
    prone to autoimmune diseases]
53
Q

how do you treat an antibody deficiency?

A

➢ Antibiotics

➢ Immunoglobulin G replacement

54
Q

what is Severe Combined Immunodeficiency (SCID)?

A

inherited abnormality in immune system

  • v high risk of infection
55
Q

which would be more severe, B cell defects or T cell defects?

A

Defects in T cells

Usually more severe since B cells also need T cell help

56
Q

SCID is due to which type of cell defect?

A

T cell defect

57
Q

no T cells would suggest which condition?

A

Severe Combined Immunodeficiency (SCID)

58
Q

what causes SCID?

A

➢ Defect/absence of critical T cell molecule

➢ Loss of communication
- MHCII deficiency
o [B-cells not able to communicate with T-cells]

➢ Metabolic
- Adenosine deaminase deficiency

59
Q

how would a defect in a phagocyte present?

A

PRR: IRAK4→ recurrent pneumonia, poor inflammatory response

60
Q

how would defects in the complement cascade present?

A

bacterial meningitis

61
Q

how would defects in antibodies present?

A

recurrent infection

62
Q

how would defects in T-cells present?

A

SCID

Clinical Pathology (RIP) (49 decks)

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