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FRACP > Immunology > Flashcards

Immunology Flashcards

1
Q

Type I hypersensitivity

  • mediators
  • examples of conditions
  • Ix
  • Tx
A 
IgE mediated (anaphylaxis and atopic disease)
Involves Mast cells

Ix - skin prick for specific IgE and RAST

Tx

  • Antihistamines (decr vasc permeability and bronchoconstriction)
  • Corticosteroids (decr inflammation)
  • Adrenaline (helps vasoconstrict)
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2
Q

Type II hypersensitivity

Mechanism

Examples of diseases

A

‘Cytotoxic’, tissue-specific

  • Antibody mediated -> target cell damage
  • Due to defective ‘central tolerance’
  • Due to self-reactive B cells that produce IgM and IgG +/- C’ activation -> attacks healthy host tissue (binds to Ag on host cells) and comes Ag-Ab complex at tissue site

Examples:

  • Goodpastures
  • Graves
  • MG
  • Rheumatoid
  • Autoimmune haemolytic anaemia
  • Haemolytic disease of newborn
  • ITP
  • Transfusion reactions
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3
Q

Central tolerance

A

Immune cells that are ‘self-reactive’ are destroyed in primary lymphoid organs (thymus for T cells and bone marrow for B cells)

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4
Q

Type II hypersensitivity: give examples of each

  1. Complement system activation
  2. Opsonisation and phagocytosis
  3. Natural killer cell activation
  4. Physical presence of Ab at receptor binding site impairs physiologic function
A
  1. Goodpastures syndrome -> Ab, C’ activation against collagen in lung and kidneys
  2. Autoimmune haemolytic anaemia; ABO, Rh-hemolytic disease of newborn
  3. Pernicious anaemia, guillain barre, Rh fever
  4. Graves disease (activation of TSH receptor -> hyperthyroidism)
    and Myasthaenia Gravis (inhibition of nicotinic Ach receptor )
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5
Q

Type III hypersensitivity

Pathophys
Mediators involved
Examples of diseases

A

Immune complexes (Ag-Ab complexes) deposit in blood vessel walls causing inflammation and blood vessel damage through complement cascade activation (note C3 and C4 used in large amounts)

ex: SLE = vasculitis in kidneys (glomerulonephritis), joints (arthritis); other forms of glomerulonephritis ; Serum sickness; Farmers lung

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6
Q

Type IV hypersensitivity

  • Mediators
  • Pathophys
  • Examples
A

T cell mediated (no Ab involved): Reaction occurs in 24-72hrs

  • > CD4 (Helper T cells): releases cytokines which attract other immune cells
  • > CD8 (Cytotoxic or ‘Killer’ T cells): directly kills things, specific targets
  • > Leads to inflammation and tissue damage

Dendritic cell presents Ag to CD4 naive T cell in LNs -> activation/ maturation into Th1 cell which releases cytokines -> attracts other immune cells which leads to local inflammation -> erythema, oedema, fever

CD4+ (helper T cell) mediated:

  • Contact dermatitis - Poison ivy and nickel allergy
  • Tuberculin skin test (reaction to Mycobacterium tuberculosis protein injection into dermis)
  • Multiple sclerosis (myelin)
  • IBD (lining of intensive)
  • GVHD

CD8+ (Killer T cells) mediated

  • Type 1 diabetes mellitus (pancreatic islet cells)
  • Hashimotos thyroiditis (thyroid epithelial cells)
  • GVHD
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7
Q

Innate immune response

  • Speed of response
  • Memory?
  • Specificity of response

What components?

A

Non-specific response (responds to molecular patterns ie PAMPs, DAMPs, rather than specific Ag)
Fast! Response in minutes to hours
No memory associated with this response (same reaction to Ag no matter how many times it is exposed)

  • Mechanical (cilia, epithelial tight jxns)
  • Chemical (ex low pH of stomach acid, enzymes, antibacterial peptides, defensives etc)
  • Microbiome
  • Cellular: monoctyes, macrophages, Neuts, eosinophils, basophils, mast cells
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8
Q

Adaptive immune response

What cells are involved

Speed of response?
Specificity?
Memory?

A

Involves B and T cells and immunoglobulins

  1. Highly specific (generation of 10^23 different T cell receptors)
  2. Slower response (~2 weeks to peak)
  3. Generation of memory (enhanced second response)

Relies on cells being primed -> differentiate into the right cell to fight that specific pathogen
Takes a few weeks
Immunologic memory -> clonal expansion of immune cells to fight the infection. on destruction of the pathogen, some of the clonal cells become plasma cells which on subsequent exposure undergo clonal expansions such that the immune response is much faster and stronger

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9
Q

Myeloid progenitor cells
Where are they made?
What cells do they differentiate into?

A

Made in bone marrow
Granulocytes
- Neutrophils
- Eosinophils
- Basophils
- Mast cells

Dendritic cells
Macrophages
Monocytes

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10
Q

Monocytes - function/role and what cells do they differentiate into?

A

Phagocytic/Ag presenting/produce cytokines

Differentiate into macrophages and dendritic cells

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11
Q

Dendritic cells
- role/purpose

A

Phagocytic/Ag presenting/produce cytokines:

Present Ag to T cells
- This connects innate to adaptive immune systems

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12
Q

Macrophages

A

Phagocytic (eat dead cells, invading pathogens)
and APC
-> Present Ag to T cells (This connects innate to adaptive immune systems)

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13
Q

Neutrophils

A

-> degranulate to produce free radicals -> direct killing

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14
Q

Eosinophils

A

-> degranulate to produce histamines and cytokines (allergy/parasites)

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15
Q

Mast cells

A

-> involved in asthma and allergic responses

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16
Q

Basophils

A

-> degranulate to produce histamine and cytokines (allergy)

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17
Q

Lymphoid progenitor cells

A

Made in bone marrow

  • NK cells
  • T cells
  • B cells
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18
Q

NK cells

A

(innate)
Complete development in bone marrow.
Degranulate to produce cytotoxic molecules that directly kill the target cell via apoptosis
Specifically against viruses

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19
Q

B cells

A
  • Adaptive immunity
  • Complete development in bone marrow
  • Live in lymph nodes
  • Bind to Ag -> present the Ag on their surface -> displays the Ag to T cells -> activates T cells which help the B cell turn into a plasma cell which can produce lots and lots of antibodies (IgM/G/E/A) against that particular Ag
  • Those Abs circulate in the blood
  • This process takes a few weeks
    Can turn into memory B cells for subsequent exposure
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20
Q

T cells

A

Adaptive immunity
- Completes development in thymus
- Naive T cells are presented an Antigen which leads it to become ‘primed’ and differentiate into
1. CD4 T cells = helper t cell, secretes cytokines that coordinate immune response against that Ag
2. CD8 T cells = cytotoxic (kill target cells)
Can turn into memory T cells for subsequent exposure

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21
Q

Where to B and T cells develop?

A

Common lymphoid progenitor cell

  • > becomes immature B cell in bone marrow, then travels to spleen to become mature plasma cell -> secrets B cell receptors
  • > some travel to thymus to differentiate into T cells
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22
Q

What part of the B cell receptor encodes the type of Ig it is?

A

The heavy chain genes encode this

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23
Q

What are the five types of Ig and what is the main role of each class?

A

IgM - 1st response -> activates C’ pathway most effectively
and doesn’t require T cell help

IgG - memory
- opsonisation + classical C’ pathway

IgA - acts at mucosal sites to prevent pathogens entering body
opsonisation

IgE - allergy mediator, induced by IL4, triggers granulocytosis of mast cells, eosinophils, basophils

IgD- helps mature B cells leave bone marrow

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24
Q

what is the main role of each class of Ig?

IgM
IgG
IgA
IgE
IgD

A

IgM - 1st response -> activates C’ pathway most effectively
and doesn’t require T cell help

IgG - memory
- opsonisation + classical C’ pathway

IgA - acts at mucosal sites to prevent pathogens entering body
opsonisation

IgE - allergy mediator, induced by IL4, triggers granulocytosis of mast cells, eosinophils, basophils

IgD- helps mature B cells leave bone marrow

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25
Q

Primary immunological response

A

B cells activated through interaction with dendritic cells (presents Ag to B cell) -> B cell presents Ag to T cell -> B cell switches from producing IgM to producing IgE/G/A etc and some become memory B cells

Ultimately you get lots of short lived effector cells and a few long-lived memory B cells
Effector cells die out after immune response ends/pathogen is eliminated

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26
Q

What is the life span of a memory B cell and where do they live?

A

Live up to 10 years in lymph node

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27
Q

What Ig classes don’t memory B cells produce

A

IgM and IgD

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28
Q

What are the 2 types of memory T cells and how long do they live/where do they live?

A

Live 25 years

Central memory T cells

  • remain in lymphoid tissue
  • undergo clonal expansion when re-exposed to pathogen

Effector memory T cells

  • circulate around body looking for pathogen
  • responds as primary immune response (CD4 and CD8 T cell response) when exposed to pathogen
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29
Q

Skin healing mechanism

A

Primary intension

  • ex: shallow epidermis cuts
  • wound edges come together
  • stem cells in epidermis are brought close together and can regenerate damaged tissue near surface (minimal scar)

Secondary intension

  • ex: tooth socks, severe burns
  • Wound edges far apart so wound replaced by connective tissue that grows from base of wound upwards

Tertiary intention

ex: dog bite injury
- Wound cleaned and left open due to increased potential for bacterial contamination (abscess/collection)
- After period of days they then heal by primary or secondary intention

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30
Q

Steps of wound healing

A
  1. Haemostasis (vasoconstriction + blood clot forms to prevent further blood loss)
  2. Inflammation
    (damaged cells released chemokine and cytokines, incr vascular permeability so attracted neutrophils and macrophages can enter area and clear foreign material and destroy pathogens -> scab formation)
  3. Epithelialization
    (Stem cells in epidermis proliferate and replace lost/damaged cells)
  4. Fibroplasia = production of granulation tissue
    [Fibroblasts in dermis proliferate and secrete collagen (fibroplasia)
    a) Collagen forms bungles which provide tensile strength
    b) Stimulates blood vessel growth (angiogenesis)]
  5. Maturation = wound gets more support
    a) collagen cross linking to incr tensile strength of wound
    b) collagen remodelling and then contraction which pulls edges of wounds together
    c) regimentation restores original pigmentation
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31
Q

BK virus

Transmission

What systems does it affect and what are its clinical effects

Ix for Diagnosis

Tx

A

Affects urinary system in immunocompromised hosts
- ex: HIV, tacrolimus (immunosuppressive medication used in transplants to suppress immune-mediated rejection)

Transmission via droplets and ingestion -> travels in blood to kidneys, stays latent in immunocompetent hosts but if immunocompromised can become reactivated

ix- viral DNA in blood and urine

Clinical effects/tx:

  • Haemmhoragic cystitis in BM transplant recipients -> tx is hydration and clot evaluation (catheter + flush)
  • Ureteral stenosis and retention (inflammation/fibrosis causing narrowing) -> tx is balloon dilation or stent
  • Nephropathy in kidney transplant recipients (secondary to inflammation -> tissue damage) -> tx is immunosuppression
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32
Q

MHC II - what cells are they found on?

A

Only on Ag presenting cells (monocytes, macrophages, dendritic cells, B cells)

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33
Q

MHC I - what cells are they found on?

A

On all nucleated cells throughout body

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34
Q

What do histocompatibility genes code for and what is their purpose

A

HLA (human leukocyte antigens) ie
MHCI and MHC II proteins which are expressed on our cells
Helps to differentiate self cells from non-self cells

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35
Q

How are transplant donors selected and why?

A

Transplant donors are selected to share as many HLA Ag with the host as possible to minimise rejection/chance of GVHD

Even with twins who are HLA
identical, minor histocompatibility Ags are recognised as foreign and can mount immune response

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36
Q

GVHD immunological mechanism

When can this be beneficial?

A

T-cell mediated transplant rejection

Donor T cells react against recipients MHC Ags which they see as ‘foreign’

  • > CD4 recognise MHCII -> recruitment immune response
  • > CD8 recognise MHCI -> direct destruction of target tissue

Common targets - skin, liver, gut

NOTE - this is seen as beneficial in leukaemia as this response helps to ELIMINATE the leukaemia recipient’s cancerous blood cell lines

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37
Q

IgE mediated Type I HS pathophys
- immediate and delayed reaction

A
  1. Sensitisation = first exposure
  2. Subsequent exposure

Pollen breathed in ->
Dendritic cells/M cells in gut/APC bind to pollen (allergen=Ag)
-> Migrates to lymph nodes and presents the Ag to T helper cells = ‘priming’
-> Differentiation of T helper cell into TH2 cell driven by IL 4,5,10 cytokines
-> TH2 cells produce IL4 which gets B cells to switch to plasma cells producing Allergen-specific IgE.
-> Also produces IL5 which induces production of eosinophils
-> Allergen-specific IgE attach to Mast cell and basophil surface

Second exposure event to allergen

  • > IgE-Coated mast cells bind to Allergen -> mast cell degranulation -> pro-inflammatory mediators including:
  • eosinophils
  • histamine -> bind to H1 receptors in bronchi -> bronchoconstiction (asthma)
  • histamine -> cause vasodilation -> airway oedema, urticaria, hypotension

Late phase reactions (8-12hrs later) induced by IL4,5,10 and leukotriene release by mast cells

  • TH2 cells
  • Basophils
  • Eosinophils
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38
Q

Molecules involved in anaphylaxis

A

Histamine -> blood vessel permeability, dilation and bronchoconstriction
Tryptase -> tissue injury
Cytokines IL 4, IL13
Leukotrienes (LTB4 and C4) - attract inflammatory cells to the area hours later (can lead to biphasic reaction)

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39
Q

Ix for allergy

A
  1. Skin Prick Tests
    - panels of up to 40 allergens are pricked into skin
    - wheal reaction
  2. RAST = blood tests look for IgE Ab against certain allergens (serum-specific IgE)
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40
Q

Erythema multiforme

what is it

cause/triggers

mx

A

When immune cells attach epithelial cells

Affects skin and MM
Often triggered by infection (HSV) or medications (anticonvulsants, abx)

Ft: targetoid lesions (central necrosis with macules, papules, vesicles and bullae
with haemmhoragic crusting of lips
Dehydration secondary to oral mucosa involvement

Mx: self-limiting,
Treat underlying cause (infection or stop any medications)
if due to HSV, can use acyclovir or valaciclovir as prevention

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41
Q

Bullous Impetigo

A

Staph aureus skin infection (‘impetigo’) leading to formation of multiple Bullae that rupture easily, leaving erosions

Most often affect face trunk, perineum and extremities

Tx - cefalexin to treat staph aureus and prevent transfer of staph between household members. Vancomycin if not responding to cef.

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42
Q

Staph scalded skin syndrome

A

Bullous impetigo in immunocompromised individuals

Widespread bullae, erosion and systemic sx (fever, malaise). Develops rapidly.

Mx - supportive care with rehydration and antipyretics + IV abx

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43
Q

DRESS (drug reaction with eosinophils and systemic symptoms)

A

Rare life threatening condition caused by medications (2-6 weeks after initiation of medication) - allopurinol, anti epileptics, sulphonamides, minocycline, vancomycin

Skin eruption leading to diffuse confluent erythema involving >50% BSA
Eosinophilia on bloods
Systemic sx: fever, malaise, lymphadenopathy with involvement of kidney, liver, lungs

mx - withdraw offending medications
- topical CS OR if severe systemic (IV) CS

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44
Q

Steven Johnson Syndrome

A

Life threatening skin reaction with systemic compromise due to autoimmune response to a medication (often anticonvulsants)

Epidermal sloughing of skin and mucous membranes involving <10% BSA
- essentially a burns reaction (macule and vesicles leading to skin sloughing)

Less severe version of Toxic epidermal necrolysis (TEN > 30% BSA)

Tx

  • Admission to burns unit or ICU
  • Cease triggering medicaitons
  • Supportive tx (IV fluids, PN)
  • Systemic immune modulators (antihistamines, IVIg, corticosteroid)
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45
Q

Risk factors for allergic rhinitis

A

Fam hx atopy
Elevated IgE by age 6
Heavy Smoking mother
Heavy Exposure to indoor allergens

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46
Q

Pathogenesis of allergic rhinitis

A

a. Exposure of an atopic host to an allergen -> IgE production
b. Bridging of IgE molecules -> mast cell activation + degranulation -> release of pre-formed inflammatory mediators (histamine, prostaglandin, leukotrienes)
c. Late phase allergic response (4-8 hours) -> eosinophils, neutrophils and mast cells infiltrate nasal mucosa -> leukotrienes, eosinophil peroxidase, major basic protein + IL-3, IL-5, GCSF

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47
Q

Sx of allergic rhinitis

And classification

A

a. Acute – sneezing, itch, rhinorrhoea (due to histamine)
b. Delayed – nasal congestion (due to infiltration inflammatory cells)

Classification

a. Episodic - <4 weeks
b. Persistent - >4 weeks
c. Mild – nil below features
d. Moderate to severe – sleep disturbance, school interruption

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48
Q

Sx of allergic rhinitis

And classification

A

a. Acute – sneezing, itch, rhinorrhoea (due to histamine)
b. Delayed – nasal congestion (due to infiltration inflammatory cells)

Classification

a. Episodic - <4 weeks
b. Persistent - >4 weeks
c. Mild – nil below features
d. Moderate to severe – sleep disturbance, school interruption

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49
Q

Tx for allergic rhinitis

A

Allergen avoidance
Nasal irrigation

Topical inhaled corticosteroids

  • 1st line for tx of allergic rhinitis (sneezing, eye sx)
  • takes 2-4 weeks for max sx benefit; needs to be continued for 2-6 months

Antihistamines (for itchy/sneeze/eye sx)

Antihistamines for SHORT TERM USE only (<3 days) in children >6 yrs
- reduces nasal congestion

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50
Q

What type of reaction is eczema/atopic dermatitis

A

Type I hypersensitivity reaction to allergen -> inflammation of skin tissue -> leaky skin tissue allows water to escape -> leads to dry skin (which is itchy ++)

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51
Q

Eczema - types of skin lesions and distribution

A

Types

a. Acute = erythematous papules
b. Subacute = erythematous, excoriated, scaling papules
c. Chronic = lichenification, fibrotic papules

Distribution

a. Infancy = face, scalp, extensor; diaper area spared
b. Older children = flexural folds

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52
Q

What syndromes is eczema a feature of?

A

Hyper IgE syndrome (Job syndrome is autosomal dominant form)

Phenylketonuria

Wiskott-Aldrich syndrome

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53
Q

Wiskott-Aldrich syndrome

  • cause
  • triad of features
  • what is the main risk?
  • tx
A

X-linked (WASP protein deficiency - req in actin polymerisation and signalling of T cells)
CD4 T cell deficiency -> impaired B cell fxn as no T cell help

Features (‘TIME’):
Thrombocytopenia (petechiae, bloody stools)
Immunodeficiency (recurrent otitis media/’draining ears’, recurrent viral infections initially, then bacterial infx more problematic over time)
Malignancy risk
Eczema

Main risk - Intracranial haemmhorage, severe infections

Definitive tx is HSCT

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54
Q

Eczema management

A

Identify/avoid triggers

  • irritants (dryness, humidity, heat, excess sweating, soap fabrics etc), foods, aeroallergents, infections
  • Keep finger nails short/stop scratching

Emollients - BD +/- wet dressings

Anti-inflammatory agents (use in bursts to clear eczema, then stop)

  • Topical steroids
  • -> face: 1% hydrocortisone
  • -> body: 0.1% methylpred (advantan fatty ointment) or 0.1% mometasone furoate (elocon)

Systemic immunosupppression

  • Azathioprine (inhibits purine synthesis)
  • Pimecrolimus ointment (calcineurin inhibitor)
  • Methotrexate (inhibits dihydrofolate reductase)

Treat infx

  • Bleach bath
  • Antibiotics/antivirals as indicated
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55
Q

What type of reaction is allergic contact dermatitis?

A

Type IV hypersensitivity reaction

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56
Q

What are the most common (super)infections to think of in eczema ?

A
  1. Bacterial
    - Staph aureus
  2. Viral
    - HSV most common
    - Enterovirus
    - Molluscum contagiosum
  3. Fungal
    - Tinea
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57
Q

MOA azathioprine

A

Immunosuppressive agent

Inhibits purine synthesis, thus decreasing production of DNA and RNA requiring for synthesis of WBC

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58
Q

Criteria for anaphylaxis

A

Note - some features are transient and resolve before arriving to medical care

  1. Acute onset with typical skin features (urticarial rash or erythema/flushing or angioedmea)

PLUS

  1. Resp/CV and/or persistent GI symptoms
    - Note: CV sx in infants can include pale/floppy and resp sx can include persistent cough or hoarse voice/change in character of cry

OR

  1. Acute onset hypotension or bronchospasm or upper airway obstruction (even in absence of typical skin features)
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59
Q

RF for fatal aasthma

A

a. Adolescence
b. Nut and shellfish allergy
c. Poorly controlled asthma
d. Delays to administration of adrenaline or emergency services

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60
Q

What is the role of tryptase blood test in anaphylaxis

A

No role in diagnosis (anaphylaxis is a CLINICAL diagnosis) unless the diagnosis is unclear (ie anaesthetic reaction)

  • take it 15min-3hrs post anaphylaxis and a second level 24 hours post
  • If level is >11.4 or elevated by 20% above baseline – diagnosis confirmed
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61
Q

MOA adrenaline

A

Adrenergic receptor agonist

Alpha-1 receptor
o Vasoconstriction + increased BP
o Reduces mucosal edema

Beta-2 receptor
o Broncho dilatation
o Reduces mediator release (Stabilises mast cells)

Beta-1 receptor
o Increases HR
o Increases cardiac contraction force

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62
Q

Pathophys serum sickness

A

Type III hypersensitivity reaction caused by Ag-Ab complexes

  • Small complexes – circulate harmlessly
  • Large complexes – cleared by reticuloendothelial system
  • Intermediate complexes = may deposit in blood vessel wall and tissues – trigger vascular (leukocystoclastic vasculitis) and tissue damage (activation of C’)
  • C3a and C5a – promote chemotaxis and adherence of neutrophils
  • Tissue injury from liberation of proteolytic enzymes and oxygen radicals

Typically in response to snake venom or insect bites (reaction to the serum proteins) OR antibiotics like cefalcor, pencilling, bactrim or anticonvulsants or like rituximab

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63
Q

Presentation of serum sickness

and treatment

A
  1. Rash (urticaria, pruritus) - initially erythematous, evolving into dusky centre with round plaques. mucous membranes NOT involved.
  2. Fever
  3. Polyarthritis/arthralgia

Beings 1-3 weeks after drug exposure, resolves in ~2 weeks (but can last up to 4 months)

Treatment
- Supportive, withdraw offending agent
- Antihistamines, NSAIDs
+/- steroids

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64
Q

Serum sickness
what type of HS reaction?
Blood test finding for serum sickness

A

Type III immune-mediated hypersensitivity run

Low C3 + C4 (nadir day 10) + total haemolytic complement (CH50)

Thrombocytopenia, neutropenia

Elevated ESR and CRP

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65
Q

How to differentiate serum sickness from a serum sickness-like reaction?

A

Serum sickness

  • low c3, c4.
  • onset 1-2 weeks post exposure to offending agent.
  • Can be assoc w systemic sx such as edema (i.e., of the hands, feet, and face), lymphadenopathy, headache or blurry vision, splenomegaly, anterior uveitis, peripheral neuropathy, nephropathy, and vasculitis, renal injury

SSLR

  • normal c’.
  • Onset 5-10d post exposure to causative agent.
  • Systemic symptoms are less likely in serum sickness-like reaction, which is usually limited to fever, arthralgias, rash/urticaria, and pruritis.
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66
Q

Henoch Scholein Purpura clinical prsentation

A

Most common vasculitis of childhood

Affects ages 2-8 most commonly

Occurs after URTI (viral or group A strep/strep throat) in 50% patients

Features

  • Purpura (palpable purpura, petechiae, ecchymoses)
  • Arthritis/arthrlgia (large joints of lower limbs)
  • Abdo pain (beware of complications of intussusception, GI haemorrhage, bowel ischaemia/necrosis/perforation)
  • Nephritis with proteinuria/haematuria, HTN
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67
Q

Ix for HSP

A

Urinalysis -> urinary protein-creatinine ratio, blood
Blood pressure

UEC
ALbumin

Consider the following if diagnosis unclear (ddx ITP, leukaemia, infx) or to identify potential complications of HSP

  • FBE
  • Blood culture/urine culture
  • Abdo imaging
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68
Q

Mx of HSP

A

Note- sx generally self-resolve within 24-72 hours (rash is last to resolve)

Mild pain - sx relief (panadol, bed rest, +/- NSAIDS if no CI)

Mod-severe pain - consider steroids (oral pred or IV methylpred with wean once sx resolved) if abdo pain, joint pain as may reduce duration of sx

F/U

  • regular follow up for the next 12 months monitoring urinalysis and BP for renal complications
  • If there is no significant renal involvement and normal urinalysis at 12 months, no further follow-up is required
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69
Q

HIV pathology

A

Targets CD4+ cells (macrophages, dendritic cells, macrophages have this on their surface)

gp120 receptor on the HIV molecule attaches to the CD4+ molecule’s coreceptor (CCR5 or CXCR4) -> injects ssRNA retrovirus (uses reverse transcriptase to make complementary strand DNA) into target cell

Results in the transcribing and translating of viral DNA by the host cell -> making lots of new viral particles

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70
Q

Tx HIV

A

Antiretroviral therapy (ART): combination of medications that work to slow HIV replication, allowing immune system time to recover and allowing it time to fight off other inhx

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71
Q

What defines AIDs

A

T cells <200 they now have AIDS
- Persistent fever, fatigue, LOW, diarrhoea

AIDS defining illnesses (PJP, recurrent bacterial pneumonia, fungal infections, certain tumours)

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72
Q

HIV natural history

A

Presentation with flu-like sx in acute infective period (with incr in HIV in blood, decr in T cells) until host immune system mounts counter attack (by 12 weeks, with decr in HIV viral load to almost undetectable and incr in T cells)
Then enters into latent/chronic phase
- however virus load gradually increasing though and T cells gradually decreasing
- opportunistic infections more common/severe

When body’s T cells reach as low as 200-500 immune system is severely compromised
- lymphadenopathy, minor infections become severe (oral candidiasis, hairy leukoplakia)

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73
Q

Transmission HIV

A

Enters body most commonly via sex (75%; M->M but also M->F in developing nations)

  • IV drug abuse
  • Mo -> fetus

CD4+ Immune cells in the peripheries take up the virus and travel to lymph nodes -> more infection of other immune cells -> spike in viral load

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74
Q

X-linked agammaglobulinaemia

Inheritance

Pathology

Presentation

Tx

A

X-linked recessive gene mutation featuring LACK of circulating B cells and antibodies of all classes (inherited and sporadic forms)

Mutation in BTK gene making Bruton’s Tyrusine Kinase enzyme ineffective which is required for B cell maturation -> no maturation occurs past pre-B cell stage so they do not leave bone marrow -> no B cells or Ig in circulation -> infections

Often presents at around 6-9 months (that’s when maternal IgG runs out)

  • no palpable LNs or tonsils on exam
  • development of infections

Ix -
Plasma - IGs very low/absent with no or few circulating B cells
+/- BM (pre B cells)
+/- GI bx (no plasma cells)
Genetics - BTK mutation

Tx - lifelong IvIg infusions -> boosts immune system and gives passive immunity
-> treat infx immediately with abx

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75
Q

Infx with X-linked agammaglobulinaemia

A

Encapsulated bacteria (strep, HIB, mycoplasma)

  • Sinopulmonary ix
  • Septic arthritis
  • OM
  • Meningitis

Viral infections

  • hepatitis
  • enterovirus
  • CNS infections with echovirus and coxsackie
  • Echovirus associated myositis
  • poliovirus -> paralysis

Fungal and some parasitic infections (Giardia)

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76
Q

Ix findings for X-linked agammaglobulinaemia

A

FBE - Neutropenia at height of infection

Flow cytometry

i. Peripheral blood B lymphocytes < 1% (demonstrated on flow cytometry), pre B cells present in bone marrow
ii. ↑ T cell percentage, normal T cell subset ratios, normal T cell function and thymus

Immunoglobulin levels

i. IgG, IgA, IgM, IgE <95% centile for age and race
ii. <100 mg/dL
iii. Isohaemagluttinins (natural Ab to type A and B polysaccharide antigens) absent
iv. Antibodies to vaccines absent

Intestinal biopsy : absence of plasma cells

Prenatal testing – can be performed on male fetuses

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77
Q

Common variable immunodeficiency (CVID)

What is it also known as?

Mode of inheritance?

What is it?

Key Features

Key Ix findings

Mx

A

IE ‘acquired hypogammaglobulinaemia’

Inheritance - AD or sporadic

Heterogenous group of cdtns characterised by hypogammaglobulinaemia with phenotypically NORMAL B cells (B cells >1%)

Normal numbers of circulating lymphocytes - do not differentiate into Ig producing cells when stimulated
-> later age of onset than XLA (late childhood/adulthood) and normal tonsils/LN

Features

  • Low IgG +/- IgM, IgA (note IgM and IgA can be normal in some)
  • Low (or normal) B cells
  • T cell number and function normal
  • Recurrent infx (HIB, pneumococcus, staphylococcus; sinopulmonary; bronchiectasis)
  • Concurrent autoimmune disease (cytopaenias)
  • Granulomatous disease
  • Risk of malignancy (lymphoreticular)
  • Chronic lung disease (COPD, bronchiectasis, interstitial pneumonia)
  • Malabsorption syndromes (+ infx such a Giardia)

Ix

  • Marked decr in levels of IgG, IgA +/- IgM
  • NORMAL B cells (may be slightly reduced)
  • Normal T cell numbers

Mx

  • IVIG
  • Abx (prophylaxis + tx)
  • Resp PT
  • Immunosuppression/modulation for autoimmune features
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78
Q

How long does maternal IgG persist for?

A

First 6-8 months of life

79
Q

Transient hypogammaglobulinaemia of Infancy

What is it?

Features

Tx

A

Delayed synthesis of immunoglobulins until after maternal IgG catabolized
- low IgG levels

Features

  • Normal Ab production to challenge (vaccination response)
  • Normal growth patterns
  • Lack of opportunistic infections – may have recurrent respiratory viral infections but generally not severe infx
  • 60% in males
  • Assoc w atopy
  • Resolves spontaneously after 4 years (by definition)

Tx

  • Consider Ab prophylaxis
  • Rarely IvIG (3-6mo trial only)
  • Monitor IgG, tends to incr w time
80
Q

What is the most common immunodeficiency disorder?

A

Selective IgA deficiency

81
Q

Causes of Selective IgA deficiency

A

Drugs
Congenital rubella or CMV
Other immunodeficiencies (DiGeorge, CVID)
–> Genetic assocation (?AD defect w variable expressivity)

Pathogenesis unknown but 45% have Anti-IgA Abs

82
Q

Associations with IgA deficiency

A

Autoimmune disease
- SLE/RA/Thyroiditis/Addisions
Allergic disease
Coeliac disease
Malignancy
CVID
IgG2 deficiency

83
Q

Presentation and Tx of selective IgA deficiency

A
  • Age >4 (takes this long for IgA to reach ‘normal’ levels, variation younger than this)
  • Often asymptomatic
  • Infections (resp, GI, urological) as per other Ab deficiency syndroomes
  • Giardiasis especially common
  • Note hx autoimmune disease, atopy
84
Q

In what Ig deficiency should IvIG NOT be given and why?

A

Selective IgA deficiency
due to risk of anaphylaxis as 45% of patients have antibodies to IgA and if IgE subtype can trigger fatal anaphylactic reaction following administration of blood products containing IgA

Note can transfuse IgG IVIG (>99% concentration) if also IgG deficiency

85
Q

What is Duncan disease also known as?

A

X-linked Lymphoproliferative Disease

86
Q

X-linked Lymphoproliferative Disease

What is it

What causes it

What is the clinical picture

Prognosis/outcome

A

Rare severe dysregulation of immune system IN RESPONSE TO EBV

  • > defective immune response leads to excessive T cell proliferation to try and kill (but can’t) and persistence of EBV infected cells
  • > Genetic predisposition

3 types:

  1. 60% Fulminant EBV infection and secondary HLH -> often fatal
  2. 30% Lymphoma (B cell lineage)
  3. 20-30% Acquired hypogammaglobulinaemia/Dysgammaglobulinaemia

Poor prognosis
Often 70% die by 10 years, 100% by 40 years

87
Q

SLE

What is it?

What causes it?

Pathophys?

A

Autoimmune disease
Type 3 hypersensitivity reaction

Combination of genetics + environmental triggers (UV radiation, cigarettes, virus, bacteria, certain meds, oestrogen)

Development of Ab against nuclear antigens (DNA, histones, other proteins) = anti ds-DNA
Forms Antigen-Ab complexes that can get into blood and deposit into vessels within kidneys, joints, heart, skin

Complexes initiates local inflammatory reaction via C’ system activation -> ultimately leads to cell apoptosis and tissue damage

88
Q

Diagnostic criteria of SLE

A

4 or more of the following:

Skin

  1. Malar Rash (butterfly rash on cheeks after sun exposure
  2. Discoid rash (chronic)
  3. Photosensitivity

Mucosa
4. Ulcers of mouth, nose

Serosa
5. Serositis (pleuritis, pericarditis/endocarditis/myocarditis)

Joints
6. Arthritis of 2+ joints

Kidneys
7. Renal disorders

Brain
8. Neuro disorders (seizures, psychosis)

Blood
9. Anaemia, thrombocytopaenia

89
Q

Autoantibodies in SLE

A

Antinuclear Ab (very sensitive but not very specific as seen in lots of other Autoimmune disease

Anti-dsDNA (specific)
Anti-Sm (highly specific) Anti-phospholipid (sensitive, not very specific)
–> can lead to antiphospholipid syndrome -> hypercoagulable state

90
Q

SLE treatment

A

Prevent - avoid triggers (sunlight etc)

Limit severity of flares

  • Corticosteroids
  • Immunosuppressants
91
Q

Superantigen pathophys and exemples of conditions

A
  • Class of antigen that results in excessive activation of the immune system
  • Causes non-specific activation of large numbers of T cells (up to 20% vs normal activation is 0.01% against normal Ag) and subsequent massive cytokine release (TNF alpha, IL1, IL6, IFN gamma) that can lead to fever, shock, and death (multi-organ failure)
    • >SAG is taken up by Ag presenting cells but skips Ag processing/presentation on MHCII molecule and instead binds outside of the MHC peptide binding groove and then also to the variable region of the TCR -> activates huge numbers of polyclonal T cells

Examples

  • Kawasaki disease
  • Acute Rheumatic fever
  • Scarlet fever (GAS)
  • Strep toxic shock syndrome (GAS)
  • Staph toxic shock syndrome
92
Q

Clinical features of Wiskott Aldrich syndrome

What is the pathophys/cause of this

What is the age of presentation and prognosis

A

‘TIME’

  • Thrombocytopenia (due to small, defective platelets)
  • Immunodeficiency
  • Malignancy risk
  • Eczema

X-linked disorder resulting in dysfunctional WASP protein
Results in impaired humeral responses to polysaccharide Antigens (Ab response)

Presents <1 yo
Survival beyond teens is rare (infections, bleeding, EBV associated malignancies are major cause of death)

Mx - monthly IVIG (variable concentration of IgG, IgA, IgM)

93
Q

What is the normal role of WASP protein and in what disorder is this disrupted

A

controls actin filaments required for micro vesicle formation downstream of protein kinase C and tyrosine kinase signalling

Wiskott Aldrich Syndrome (x-linked mutation in the gene coding for this protein)

94
Q

What Ig are involved in the formation of immune complexes in the classic C’ pthway?

A

IgM, IgG

95
Q

What T cells and cytokines drive the allergic response/igE etc?

A

TH2 cells

Driven by: IL4

Produces: IL4,5,13

Function: stimulates IgE, mast and eosinophils and allergic disease

96
Q

What cytokines/T cells activate macrophages?

A

TH1

Driven by IL12, IFN gamma

Produces: IFN gamma (amplifies response)

Function: activate macrophages

97
Q

What cytokines/t cells are involved in neutrophil recruitment?

A

Th17 cells

Driven by IL1, IL6, TGFbeta

Produces IL17, IL22, IL21

Recruits leucocytes, mainly neutrophils, to sites of infection -> defence of extracellular bacteria, fungal

98
Q

Recurrent sinopulmonary infx -> bronchiectasis
Hb, strep pneum, pyogenic bacteria, enterovirus

What immune defect?

A

B cell

99
Q 
Neisseria 
Pyogenic bacteria (strep, HIB)

What immune defect?

A

C’ defect

100
Q

Gingivitis

what immune defect?

A

Neutrophil defect

101
Q

PJP/other fungal infx are red flag for what immune defect?

What is prophylaxis for this?

A

T cell defect

Bactrim

102
Q

What type of immune cells are removed from the graft prior to giving HSCT to limit GVHD?

A

T cells as aGVHD is T-cell mediated

103
Q

What medications must be withheld prior to SPT?

A

Antihistamines for 1 week
Topical CS - avoid skin area

104
Q

Chronic mucocutaneous candiadias
Cause/genetics
Clinical picture
Associated condition(s)

A

< 5yo
Chronic severe candida skin and mucous membrane infx (absence of systemic infections)
- T cell defect
- mutation in AIRE (AR) or STAT1 (dominant) gene
- often assoc w endocrinopathies
- diagnosis based on skin scrapings, diagnostic testing

105
Q

SCID

Clinical picture
and ix

A

Presents early (0-6mo)

  • Severe infections
  • Persistent mucocutaneous candiadisis (thrush), PJP, EBV
  • Chronic diarrhoea
  • FTT

Ix

  • Lymphopenia (low CD3, 4 and 8)
  • Absent T lymphocytes
  • Low Ig levels (IgG lowest)
106
Q

Physiology of contrast allergy

A

No single pathogenic mechanism has been defined, but it is likely that mast cell activation accounts for the majority of these reactions. Complement activation has also been described.

107
Q

Cause of recurrent angioedema without wheals /urticaria/pruritis

A

C1 esterase deficiency
= hereditary angioedema

108
Q

Job syndrome

Alternative name?
Pathophys
Sx
What differentiates this condition from severe atopic dermatitis?

A

= hyper IgE syndrome

Pathophys

  • Impaired Th17 differentiation/function -> decreased IL 17.
  • T cell dysfunction and extremely high levels of serum IgE and eosinophils.
  • Results in decr protection against extracellular pathogens inc staph and aspergillus

Features: FATED

  • Face - coarse features
  • Abscesses (staph Aureus, aspergillus; abscesses differentiates it from atopic dermatitis)
  • Teeth retention (primary teeth)
  • Eosinophilia
  • Derm (eczema)
109
Q

HLH

What is it?

Causes

Criteria for diagnosis

Tx

A

Excessive macrophage activity -> elevated IGN-g and other cytokine levels -> excessive inflammation and tissue destruction

Primary (genetic) 
vs secondary (secondary to infection, lymphoid malignancy, systemic onset JIA)

Fever
Splenomegaly
Cytopenia of at least 2 lineages
High ferritin in > 2000
Low fibrinogen (activated macrophages consume this)
High CD25

Tx - steroids +/- cox, but

110
Q

Features of Ig deficiency disorders (general)

A

Sinopulmonary infx
Encapsulated bacterial infx - septicaemia
Predisposition to bronchiectasis if immunoglobulin untreated
Incr (CVID) or absent lymphoid tissue (XLA)

111
Q

Initial ix for Ab deficiencies

A

IgG, IgA, IgM, IgE
Test of Ab FUNCTION
- response to vaccines (measure Ab levels right after vaccination and 4 weeks post)
–>tetanus, diphtheria, HIB, pneumococcal Ab
–>Isoagglutinins, ASOT

IgG subclasses 
B cell enumeration (class switching etc)
112
Q

Rituximab

MOA

Pre-mx Ix

A

Anti CD20 (B cell killer)

Pre-mx Ix

  • IgG/A/M
  • B cell enumeration
113
Q

Severe Combined immuno deficiency (SCID)

A

X linked or AR
Severe and fatal if not recognised and treated early
Absence of adaptive immune response (T cells-defective which impacts B cell function and Ab production)

Born well at birth but FTT over first few months
Present 4-6mo w resp infx, chronic diarrhoea, chronic nappy area thrush
Bacterial infx less common due to maternal IgG up to 6mo

OE
No lymphoid tissue
Wasted but preserved HC
Resp sx
Abdo distension
Persistent diarrhoea (incl diarrhoea from rotavirus vaccine)
Oral/Nappy area thrush

Ix
Persistent lymphopaenia
-> Low T +/- B cells
Hypogammaglobuliaemia (except maternal IgG)
Thin mediastinum on CXR due to no thymus

114
Q

Causes of secondary Ab deficiency

A

Protein loss
- PLE
- Chlothorax
- Nephrotic syndrome
Drugs
- Steroid
- Rituximab

115
Q

Infant with Rash - progressive, resistant to tx
Lose hair, eyebrows
FTT
Irritable++
Lymphadenopathy, hepatosplenomegaly
Severe, recurrent infx (resp)

Eosinophilia and high IgE with lymphocytosis

A

Omenn syndrome (RAG1, RAG2 gene mutations)

Form of SCID
Presents in infany

116
Q

initial ix for SCID

A

TREC (screening)
FBE (lymphocyte count - low absolute count; abnormal lymphocyte subpopulations)
CXR (?mediastinum thin)
Flow cytometry for lymphocyte subsets (T, B and NK cell numbers) and naive T cells
Ig G/A/M/E

117
Q

Most common genetic cause of scid

A

Common gamma chain SCID
- mutation in CGC of IL2 receptor

X-linked

118
Q

Genetic mutations that can present as SCID

A

Common gamma chain mutation of IL2R

V(D)J recombination -> at TCR and BCR gene loci

ADA (adenine deaminase deficiency) -> premature death of lymphocyte precursors -> progressive loss of T/B cells
- also neurological involvement

PNP deficiency (same pathway as above)

MHCII deficiency

22q11 (complete DiGeorge)

ZAP-70 kinase deficiency (signalling molecule downstream from T cell receptor)

119
Q

Treatment of SCID

A

Supportive care
Tx of infections
HSCT
Gene therapy (up and coming)
Thymic transplant for complete Di George

120
Q

DiGeorge syndrome

A

22q11 (de novo mutation or AD)
KEY: Affects Thymic development (and thus reduction in mature T cells/deficiency in T cell mediated immunity)
‘Complete’ Di George = Complete absence of thymus

Features;
- Lymphopaenia (specifically CD3, CD4 > CD8)
- Low PHA response (=t cell response)
- Ig levels usually normal
- Variation in immune function (from near normal to SCID)
- Cardiac defects
- Characteristic facies
cleft palate
- Behaviour difficulties

Mild

  • prophylactic Ab +/- Ig replacement
  • SCID: thymic transplant is curative
121
Q

CHARGE syndrome

A

Impacts thymic development -> variable range in immune development (SCID to mild ID)

Features include

  • coloboma
  • heart anomolies
  • choanal atresia
  • retardation
  • genital anomalies
  • ear anomalies
122
Q

Ataxia telangiectasia

A

AR mutation in ATM -> DNA repair defect
First presents with progressive cerebellar ataxia ~toddler
Ocululomotor apraxia
Telangiectasia appears age 5-8
Variable immunological phenotype (Ab deficiency +/- impaired T cell immunity)
Progressive lymphopaenia with Ab decency
Malignancy risk (p53) -> early death

123
Q

HyperIgm
- what is the most common form

  • presentation
  • ix
  • mx
A 
CD40L deficiency (expressed on activated CD4+ T lymphocytes) 
X-linked 
Pathophys:
- due to defective CD40 ligand on T cells, B cells are unable to class switch from IgM to other iG classes so unable to produce longer lasting immunity

Presentation

  • presents mostly before age of 1
  • Sinopulmonary bacterial infections (humeral immune deficiency)
  • Opportunistic infections (T cell immunity) - PCP is a big one, CMV, cryptosporidiosis, sclerosing cholangitis
  • Autoimmunity
  • Malignancy (HCC)

ix

  • reduced IgG, igE, IgA production
  • 50% - elevated IgM at presentation
  • CD40 ligand flow cytometry
  • Memory B cells absent or severely reduce in number

Mx - HSCT

124
Q

Job’s syndrome - what gene mutation causes this?

A 
'Hyper IgE syndrome'
STAT3 mutation (AD or de novo) affects function of Th17 cells (neutrophil recruitment)

DOCK8 = AR form, assoc w molluscum contagiosum infx

Predisponisition to cutaneous fungal and bacterial infx

Presentation

  • Delayed loss of primary teeth
  • Poor vaccine resonse
  • Bacterial infections (staph pneumonia w abscess)
  • fungal infx (aspergillus lung infx)
  • eczema
125
Q

Chronic severe molluscum infection
- assoc w what immunodeficiency?

A

Job’s syndrome/Hyper IgE syndrome, AR form caused by DOCK 8 mutation

126
Q

Roles of complement pathway

A

Phagocytosis of microbe
Recruitment and activation of leukocytes -> Destruction of microbes by leukocytosis
Formation of MAC complex -> Osmotic lysis of microbe

127
Q

What mediators of C’ pathway recruit inflammatory cells

A

C3a
C5a

128
Q

Complement pathways
- what are the three?

Where do they converge?

What happens after they converge?

A
  • *1. Classic pathway** (IgM or IgG Ab-Ag complexes) - encapsulated pathogens (S pneumo, HIB)
  • C1q binds Fc of IgG or IgM to form C1 complex. that cleaves C4-> C4a/b which cleaves C2 to C2a/b
  • C2a binds C4b, forms C3 convertase which goes to common pathway

2. Lectin pathway (serum lectin binds mannose on pathogens) - fungal, salmonella, listeria

  • Ab independent (involves PAMPS and MBL)

3. Alternative pathway (amplification) - Neisseria meningititis

  • Requires Factor B, D and properdin to form the C3 convertase that enters common pathway

Common pathway

C3 then cleaved by C3 convertase into C3 a and C3b

  1. C3a -> recruits inflammatory cells
  2. C3b cleaves C5 to C5a/b
    - > amplification via alternative pathway
    - > triggers production of MAC (c6 to c9)

-> MAC creates pore in pathogen cell membrane -> apoptosis/lysis

129
Q

Low C4 +/- Low C3 - within what C’ pathway does the problem lie?

A

Classical

130
Q

Low C3, normal C4 - within what C’ pathway does the problem lie?

A

Alternative pathway problem

131
Q

Classic pathway deficiencies - list 2

A

Deficiency in components (C1, C2, C4) predisposes to SLE

Deficiency in C1 esterase inhibitor leads to uncontrolled activation of pathway -> Hereditary angioedema

132
Q

Pathophys of hereditary angioedema

What is the key distinguishing feature from an Ig-E driven angioedmea?

A

Deficiency in C1 esterase inhibitor leads to uncontrolled activation of pathway -> Hereditary angioedema

Incr activation of factor XII and production of bradykinins -> incr vasc permeability and angioedema

133
Q

What do alternative pathway deficiencies lead to?

A

Component deficiencies (Properdin, factor B, factor D) lead to susceptibility to encapsulated infections (Strep pneumonia, NEISSERIA, HIB, )

Control protein deficiencies lead to uncontrolled activation of alt pathway -> atypical HUS

134
Q

Presentation and treatment of hereditary angio-oedema

A

Presentation:
‘Attacks’ - skin/GI/airway, bradykinin driven by overacrtivation of Classic C’ pathway
NO urticarial rash as not mast cell driven. May have a rash called erythema marginatum, but looks different and is NOT itchy.

Mx - must carry action plan

a) Mild/cutaneous: tranexamic acid, Danazol
b) Severe: C1 esterase inhibitor (IV) concentrate, FFP or bradykinin antagonist

135
Q

Ix for C’ function

A

C3, C4

  • If C3 low with normal C4, think alternative pathway
  • If C4 low with normal C3, think classic pathway

Complement function

  • CH50 (if 0, think classic pathway deficiency)
  • AP50 (if 0, think alternative pathway deficiency)
  • If CH50 and AP50 0 - think MAC complex deficiency

For hereditary angioedema
- C1 esterase inhibitor level

136
Q

Functions of neutrophils

A
  1. Interaction with pathogen
    - direct
    - indirect (opsonisation of microbes via FcR or C’ R)
  2. Phagosome formation via fusion of neutrophil granules
  3. Product ‘NETS’ (neutrophil extracellular traps)
137
Q

Chronic granulomatous disease

Genetics

Pathophys

Presentation

Mx

A

X-linked OR AR forms

Defects in genes that encode the phagocyte NADPH oxide enzyme complex
-> inability for neutrophils to destroy the pathogens they have phagocytosed

Presentation:

  • Bacterial, fungal infx
  • Granuloma formation
  • Classically present with SUPPURATIVE ADENITIS OR ABSCESSES
  • *Classically Liver abscess-> CGD until proven otherwise*)

Problems with catalase positive organisms (Staph, Mould/aspergillus, Nocardia, Burkholderia)

Ix - Respiratory burst studies

Mx

  • Bacterial and fungal prophylaxis (bactrim and itraconazole)
  • Aggressive mx of infections
  • Monitor for disease complications (IBD)
  • HSCT is curative (survival to middle ages without this, AR>X-linked)
138
Q

Leukocyte adhesion deficiency

What is it/inheritance

Clinical features

Mx

A

AR inheritance
- 3 forms with different mutations in different components involved in leukocyte trafficking

Clinical features

  • Absent pus formation and POOR WOUND HEALING
  • DELAYED cord separation
  • Peripheral leucocytosis with associated neutrophilia
  • Recurrent bacterial infection (staph, pseudomonas, gram negative infections)

Mx

  • Aggressive tx of infx
  • HSCT is curative
139
Q

Innate immune system

  • What cells are involved
  • What molecules are involved
A

Involves myeloid progenitor cell offspring

  • Neutrophils
  • Monocytes
  • Macrophages
  • Mast cells
  • NK cells

Molecules

  • Cytokines
  • Chemokines
  • Complement
  • Coagulation proteins
140
Q

What is the role of TLRs?

A

Recognise conserved microbial molecules
Both inside and outside cells
-> TLR 1-9
-> Signal infection presence, not specific
-> activate inflammatory cytokines (IL1, IL6, TNF alpha)
-> vasodilation, incr vasc permeability (=heat, swelling, redness) and inflammatory cells migrate into tissues, releasing mediators (pain)

Important role in activating adaptive immune system if innate doesn’t get job done.

141
Q

Outcomes of acute innate response activation : SIRS response

A

Liver: CRP, mannan-binding lectin
Bone marrow: Neut mobilisation -> phagocytosis
Hypothalamus: Mount fever
Fat, muscle: protein and energy mobilisation
B and T lymphocytes: incr activation

142
Q

How do leukocytes know where to go?

A

Follow chemokines (small molecules that attract leukocytes, guide migration around body)

Other molecules within tissues further guide migration
Selectins
Integrins
ICAM

143
Q

C1 esterase inhibitor deficiency leads to what condition?

A

Hereditary angioedema (uncontrolled activation of classical C’ pathway)

144
Q

MHCI molecules are present on what cell type?
What do they process?
What cells are they found on?

A

Found on APCs

Process Viral/intracellular proteins

Bind to CD8+ T cells

145
Q

MHCII molecules are present on what cell type? What do they process?
What cells are they found on?

A

Found on Ag presenting cells: DCs, B cells, macrophages

Bind to CD4+ T cells
Bacterial/extracellular proteins

146
Q

Signals involved in activation of APCs and T cells essential for adaptive immune response

A

Signal 1: Dendritic cell is activated via TLR ligands, DAMPS, PRRs

Signal 2: Ag peptides are processed and presented by MHC molecule on APC

Signal 3: CD40, CD80 and CD86 bind their receptor on T cell

Signal 4: T cell subset differentiating cytokines (induced by PAMPs, DAMPs)

147
Q

CD4+ T cells
Role

vs CD8+ T cells
Role

A

‘Helper’ T cells (4x2):

  1. Recruit phagocytes (macrophages and neutrophils) to eat bacteria
  2. Differentiate into Th1, Th2, Th17 adn Treg cells

—> Th1 ( macrophage activation)

–> Th2 (IgE, eosinophils, mast cell activation)

–> Th17 (neutrophil recruitment)

  • -> T reg cells
    3. Bind MHCII on APCs

‘Cytotoxic’ T cells (8x1):

  1. Direct killing of targeted cells/microbes using performs, granzymes
  2. Bind MHCI on APCs
148
Q

Development of T and B cells

A
  1. Common lymphoid progenitor
  2. If it expresses a pre B or T cell receptor then it goes onto further maturation
  3. Expresses Ag receptor
  4. Proliferation
  5. Positive and negative selection depends on strength of Ag receptor (if too strong -> dies as predisposes to autoimmunity. If no response -> also dies)
149
Q

Humoral vs cellular immunity

A

Humoral: B cells and Abs

Cellular: T cells

150
Q

What is the key factor that leads to diversity in lymphocytes

A

V(D)J recombination of B and T cell receptors

151
Q

Which imune cell and cytokine(s) is involved in formation of germinal centre and class switching)

A

Follicular helper t cells (Driven by BCL 6 and IL21)

-> Produces IL21 (important for B cell function -> formation of germinal centre and class switching)

152
Q

Regulatory T cells

What is their role and what cytokines do they produce?

A

Down-modulate immune response
Suppress CD4 and CD8 T cells, B cells and NK cells

Produce TGF beta, IL10

153
Q

Mutation in ? can predispose children to early onset IBD and severe autoimmunity

A

Mutation in IL10 (foxp3) expressed by T reg cells

154
Q

Kostmann syndome

What is it?
Genetics
What does it cause?
Presentation
Tx

A

=’Severe Congenital Neutropaenia’

Causes arrest in myeloid maturation at the promyelocyte stage in the bone marrow -> neutropenia +/- monocytosis, eosinophilia

Genetics: AD (ELANE mutation, 50-60% cases) and AR (HAX1) forms

Presents w severe neutropenia usually in first mo of life

  • No dysmorphic features
  • Propensity for infections (skin infx, pneumonia, perirectal accesses, oral ulcers, gingivitis)

Tx - GCSF, HSCT

155
Q

What is PHA skin test response a marker of?

A

Screening test for cellular mediated (T Cell mediated) immunocompetence

156
Q

Red man syndrome

What is it most often triggered by?

What is the pathophys?

Tx?

A

Vancomycin

This syndrome is caused by nonspecific histamine release and is most commonly described with administration of intravenous vancomycin.

It can be prevented by slowing the vancomycin infusion rate or by preadministration of H1-blockers

157
Q

Insect bites
What is the tx for the following:
- local reaction
- large local reaction
- anaphylaxis

A
  • local: remove stinger, cold compress
  • large local: as above + oral pred + NSAID (pain) + antihistamine (itch)
  • -> 7% risk of anaphylaxis w future stings
  • anaphylaxis: adrenaline etc
  • -> venom immunotherapy indicated for anphylaxis and generalised urticaria to bite
158
Q

Gingivitis = problem with what part of immune system?

A

Neutrophil function

159
Q

Diagnosis (ix) of chronic granulomatous disease

A

a flow cytometric dihydrorhodamine neutrophil respiratory burst assay is a quick and cost-effective way to evaluate NADPH oxidase function

160
Q

what is role of C3b in c’ pathway

A

opsonisation (coating of Ag with Ab and C’)

161
Q

what is role of C5a in c’ pathway

A

Neutrophil chemotaxis

162
Q

what is role of C5b-C9 in c’ pathway

A

cytolysis (cell apoptosis) by MAC

163
Q

Role of IFNs

A

Viral infections (alpha, beta, gamma)

164
Q

Encapsulated organisms

A

Psudomonas
Strep pneumoniae
H influenzae B
N meningiditis
E coli
Salmonella
Klebsiella

165
Q

ALL Ig subclasses are low
Very low or absent B cells
Recurrent bacterial infections (sinusitis, OM, pneumonia) after 6mo of age
Small or absent tonsils, adenoids

?diagnosis
?cause

A

X-linked agammaglobulinaemia

BTK gene mutation - necessary for successful B cell expansion and maturation

tx - IVIG infusions

166
Q

Young adult with recurrent sinopulmonary and GI infections with enlarged tonsils or LN

Normal B cell counts
Low IgA, IgG, IgM

Diagnosis?
Cause?
Associations
Tx

A

Common variable immunodeficiency
B cells unable to differentiate into Ig producing plasma cells
Prone to resp infections (H influenzae, S pneumoniae, M catarrhalis, S aureus, PCP, M pneumoniae) and GI infections (giardiasis)
Can be associated w lymphoma and GI malignancies as well as autoimmune diseases (pernicious anaemia, haemolytic anaemia, thrombocytopenia, leucopenia)

tx - Ig replacement, cimetidine can help to incr IgG

167
Q

Reduced or absent IgA +/- IgG levels
Increased IgM

Diagnosis?
Sx
Association

A

Seletive IgA deficiency

Intestinal giardiasis common - chronic diarrhoea
Recurrent respiratory infections
Recurrent urogenital infections
Note may be asymptomatic

Associated autoimmune disease
Transfusion reactions common - develop serum Ab to IgA in the blood and IgE can cause fatal anaphylaxis

168
Q

what condition is associated with a high rate of anaphylaxis to blood products?

A

Selective IgA deficiency
-> need 5x washed OR blood products from IgA deficient donors

169
Q

7month ex-prem infant
Recurrent respiratory infections (none severe/life threatening)

Normal B and T cell numbers
Low IgG and IgA levels
Normal vaccine responses

?diagnosis and prognosis

A
  • Transient Hypergammaglobulinaemia of Infancy
  • defined in infants over 6 months of age whose IgG (+/- IgM, IgA) is significantly lower (less than 2 standard deviations) than 97% of infants at the same age.
  • This most commonly is corrected by 24 months of age but may persist for a few more years.
  • However the ability of these infants to make antibodies is frequently near normal and most of the patients are not unusually susceptible to infection.
  • Have NORMAL vaccine response
170
Q

What is the most common form of IgG subclass deficiency in children?
And what sort of infections does this predispose the child to?
What other immune deficiency is it associated with
Response to vaccines?
Treatment

A

IgG2

  • > predisposed to encapsulated bacterial infections (strep pneumoniae, HIB, meningococcus)
  • > often p/w recurrent sinopulm infections (don’t make them that sick) +/- meningitis +/- bacteraemia

Normal total levels of IgG but low specific subclass (IG1-4)
Can be associated with IgA deficiency as well

Poor or partial responses to pneumococcal polysaccharide vaccines

Treatment - abx prophylaxis, IVIG for severe infections only

171
Q

Severe infectious mononucleosis (EBV) infection leading to fulminant hepatitis and liver failure in a 5 year old male.

What is the diagnosis?

What else can happen? Acutely and chronically

A

Duncan disease or X-linked lymphoproliferative syndrome

Abnormal immune response to EBV infection leading to
Acutely
1. Liver necrosis and failure
2. Aplastic crisis
Chronic
3. B cell lymphomas (Burkitt lymphoma)
4. Acquired hypogammaglobulinaemia

Treatment

  • IVIG
  • Abx
  • Stem cell transplant
172
Q

What is the immunodeficiency associated with DiGeorge syndrome?
Infections associated?

A

Thymic hypoplasia

  • > Decr number and function of T cells (directly correlates with degree of thymic hypoplasia)
  • > Reduced PHA (measures proliferation of T cells)
  • > low absolute lymphocyte count

T cell defect -> Fungi and PJP

173
Q

Role of PHA

A

T cell proliferation

174
Q

1 month old presents with FTT, recurrent viral respiratory infections, eczematous rash and chronic diarrhoea
She also has recurrent oral thrush

What is the diagnosis/immune defect?
What is treatment

A

SCID

  • Impaired function of T cells and/or B cells FROM BIRTH (low #s of both)
  • -> even if normal B cell numbers, you don’t have T cells to help B cells and enable class switching so don’t produce Ig (hypogammaglobulinaemia)
  • Will have absent thymus, adenoids, tonsils
  • *red flag is pneumocystis pneumonia*

Treatment is stem cell transplant, ideally within first 3 months of life

175
Q

Boy with history of refractory eczema cx by recurrent staph infections presents with skin abscess

He has coarse facial features and has retained his primary teeth

what is the diagnosis?
What is the inheritance?
What is the underlying immune defect?

A

Job /hyper IgE syndrome

Autosomal dominant

Immune defect: Very high levels of IgE (>1000) and hypereosinophilia
T cell abnormalities and impaired neutrophil locomotion

Tx: penicillin prophylaxis, I&D abscess, gammaglobulin infusions if deficient

176
Q

Boy with thrombocytopenia at birth
Severe eczema
Recurrent sinopulmonary infections/meningitis

What is the diagnosis/underlying immune deficiency
Whatare they predisposed to?

A

Wiskott-Aldrich syndrome (X-linked recessive)

  • > Progressive T lymphocyte deficiency
  • > Progressive Ab production (normal initially, then IgM is first to reduce)

Progression to encapsulated organisms, HSV, VZV, PCP
Predisposition to lymphoma/leukaemia and autoimmune diseases

177
Q

Progressive ataxia first noticed when child starts to walk
Telangiectasia to sun exposed areas onset from 3 years of age
Recurent sinopulmonary infections

What is the diagnosis/immune defect?
Other associations?
Tx

A

Ataxia Telangiectasia (AR, ATM mutation)

  • > impaired cell mediated immunity (T cell numbers and function) and impaired Ab production (IgA > IgE and IgG)
  • > due to abnormal DNA repair

Assocations

  • Lymphomas and adenocarcinomas
  • Hypogonadism/incomplete sexual development
  • Premature ageing
  • Glucose intolerance/diabetes

Treatment

  • Avoid exposure to radiation when possible (MRI for pulm monitoring; X-rays only in acute setting)
  • Abx prophylaxis
  • Vaccination if can generate Ab response
  • IV gammaglobulin if hypogammaglobulinemia or impaired specific antibody production, or who do not tolerate or fail therapy with antibiotics
178
Q

Recurrent respiratory infections with small tonsils and profound NEUTROPAENIA

Immunological ix reveal

  • Low/absent IgG, IgA, IgE
  • Normal/high IgM
  • Normal T and B cells

What is the diagnosis and underlying immune deficiency?

A

X-linked hyper IgM
Immune defect - Impaired Ab formation due to absent CD40 ligand on T cells (B cells require this for isotope switching)

179
Q

Infant with liver abscess and hepatomegaly presents
Staph aureus is cultured from the aspirate fluid

What is the diagnosis?
What is the immune defect?
What investigations do you order to make the diagnosis?
Treatment?

A

Chronic granulomatous disease
Caused by defective/absent NADPH oxidase enzyme which is involved in killing bacteria and fungi -> results in chronic inflammation and granuloma formation

Ix: flow cytometric dihydrorhodamine (DHR) neutrophil respiratory burst assay as the gold standard

  • or Nitroblue tetrazolium test
  • Biopsy shows granuloma
  • Hypogammaglobulinaemia

Tx: gamma- IFN, Abx (prophylaxis and acute tx), neutrophil transfusions.
CURE with HSCT

180
Q

Recurrent staph skin infections + abscess
ALBINISM (skin and eyes)
Easy bleeding and bruising from plt malfunction

Diagnosis? Immune defect?
Tx?

A

Chediak-Higashi syndrome

Immune defect: neutropenia and defective neutrophil degranulation, defective granulocyte mobility and chemotaxis

Diagnosis: blood smear showing giant inclusions within leukocytes and/or by the identification of biallelic pathogenic variants in LYST on molecular genetic testing.

Tx: high dose ascorbic acid, abx, HSCT is curative

181
Q

Short stature, steatthorea (pancreatic exocrine failure), cyclical neutropenia +/- anaemia and thrombocytopenia

diagnosis?
Tx?

A

Schwachman-Diamond syndrome

Tx - Pancreatic enzyme supplementation, GMCSF

182
Q

Leukocytosis
Delayed cord separation
Recurrent gram positive and negative infections
Chronic ulcers

Diagnosis?
Ix?
Tx?

A

Diagnosis is LAD
-> abnormal leucocyte adhesion

Have peripheral neutrophilia (>12000) /leucocytosis
Ix - flow cytometry and neutrophil chemotaxis studies
Tx - BMT, abx prophylaxis

183
Q

Neisseria infection
- what is the underlying immune deficiency

A

Complement lytic pathway (C5-9)

184
Q

A child with recurrent infections, short stature and an erythematous photosensitive facial rash.
What is this condition and what population is it most common in?
What risk does it carry for future?

A 
Bloom syndrome (mutation in BLM gene -\> defective DNA repair)
- photosensitive rash +/- cafe au lait spots and immunodeficiency and dysmorphic ft (incl polydactyly)

Common in Ashkenazi Jewish population

Risk of malignancy (leukaemias, lymphomas, GIT tumours) and insulin-resistant diabetes

185
Q

A child with recurrent infections, short stature, presents with peri-orbital oedema, proteinuria and has low albumin

what is this condition?

A

Schimke immuneouseous dysplasia

  • > AR disorder
  • > presents with: short stature, spondyloepiphyseal dysplasia, immunodeficiency and progressive renal failure. Children may also have skin and eye abnormalities.
  • > develop nephrotic syndrome secondary to FSGS and will progress to ESRF
  • > prone to strokes (cerebral ischaemia +/- assoc Moyamoya) -> common cause of death
186
Q

When should women planning on getting pregnant get vaccinated w rubella and why?

A
  • pregnancy is contraindication to rubella vaccine administration
  • rubella vaccine virus may cross the placenta and infect fetus (1% chance)
  • however, there have been NO cases of congenital rubella syndrome reported in women inadvertently vaccinated in early pregnancy
  • given the theoretical risk, women are advised to avoid pregnancy for 28 days following vaccination
187
Q

13mo child with recurrent sinopulmonary infections and an episode of HSV 1
Normal lymphocyte count but NEUTROPENIC during infection
Low IgG and IgA and normal IgM levels
Normal T and B cell levels and normal T cell proliferation response
No evidence of vaccine response however despite being fully vaccinated

What is the diagnosis?
What is the underlying pathophys?

A

Hyper-IgM

70% Cases X-lined (mutation in XHIM resulting in abnormal T helper cell CD40 ligand)

  • > normally, in the presence of cytokines, CD40 interacts with B cells and signals them to switch from producing IgM to producing IgA, IgG, or IgE).
  • > In X-linked hyper-IgM syndrome, T cells lack functional CD40 ligand and cannot signal B cells to switch.
  • > Thus, B cells produce only IgM; IgM levels may be normal or elevated.
  • > Patients with this form may have SEVERE NEUTROPENIA and often present during infancy with Pneumocystis jirovecii pneumonia (or other opportunistic infections).
  • > Otherwise, clinical presentation is similar to that of X-linked agammaglobulinemia and includes recurrent pyogenic bacterial sinopulmonary infections during the first 2 yrs of life.
188
Q

The Apidae family (honey bees) and the Vespidae family (yellow jackets, yellow hornets, white-faced hornets, and paper wasps) belong to the order Hymenoptera and account for most of the stings that lead to anaphylactic reactions. The stings are usually painful.

  1. What is the risk of recurrence following anaphylaxis to bee/wasp stings?
  2. What reduces risk of recurrence and by how much?
  3. Does family history impact risk of anaphylaxis?
  4. What is the role of venom-specific IgE screening?
A

Children who have had a previous anaphylactic reaction have a 30% risk of recurrence.
-> People with LOCAL reactions have a low risk of a future anaphylactic reaction.

Venom Immunothreapy is safe and highly effective – reducing to risk to 5%.

A family history does not put a child at increased risk – the risk of anaphylaxis is <1%.
Venom specific IgE is not indicated because it is common to have a positive test but not to exhibit symptoms when exposed.

189
Q

What is the most common immunodeficiency and what is the prevalence?

A

IgA deficiency
1:500; most are asymptomatic.
Symptoms can be seen at any age; typically sinopulmonary infections; increased risk of allergy, autoimmune disease, and anaphylaxis from blood products.

190
Q

A child with eczema, recurrent infections and recombinase activating gene 1 (RAG1) defect.

?diagnosis?

A

Omenn syndrome is a variant of SCID (severe combined immunodeficiency).

Children present with recurrent infections, exudative erythroderma, lymphadenopathy, hepatosplenomegaly, chronic persistent diarrhoea, and failure to thrive.

191
Q

A child with eczema, recurrent infections, raised serum immunoglobulin E (IgE) , allergies and trichorrhexis invaginat.

diagnosis? Mutation?

A

Netherton syndrome
Trichorrhexis invaginata of hair is also known as “bamboo hair” and is pathognomonic of Netherton syndrome.
Caused by SPINK5 mutation causing corneal

192
Q

Which vaccines are live vaccines?

A

Varicella and MMR vaccines are live vaccines.
The later oral polio vaccine (Sabin) was a live-attenuated vaccine.
-> The injectable polio vaccine (Salk) is the original inactivated (dead) poliovirus vaccine.

193
Q

A four-year-old boy presents with a long history of recurrent febrile episodes associated with mouth ulcers, diarrhoea, fatigue and bleeding gums.

Diagnosis?

Ix for diagnosis

A

Cyclical neutropenia

  • > A rare autosomal dominant disorder in which neutrophil counts oscillate between 0.1 and 1.5 every 21 days.
  • > Neutropenic periods last 3-6 days accompanied by malaise, anorexia, fever, lymphadenopathy and mucosal ulceration (stomatitis, gingivitis, periodontitis).

Ix: Neutrophil counts twice weekly for a minimum of 6 weeks.

194
Q

Most common food allergies

Which persist vs which do children grow out of?

A
  1. Egg
  2. Cow’s milk
  3. Peanuts
  4. Tree nuts (e.g.cashews)
  5. Then wheat, soy, fish, shellfish and sesame

Nuts/seafood – tends to persist; review every 5 years

–> around 20 per cent of children outgrow their peanut allergy by the time they are teenagers,

–> 10 per cent will outgrow a tree nut allergy

Egg, wheat, milk – vast majority outgrow their allergies; review 12-18 months

FRACP (21 decks)

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