Immunology Flashcards
1
Q
What is an allergy?
A
Hypersensitivity of the immune system to allergens
2
Q
What are allergens?
A
Proteins that the immune system recognises as foreign and potentially harmful
3
Q
What is atopy?
A
Predisposition to having hypersensitivity reactions to allergens
4
Q
What are the atopic conditions?
A
Eczema Asthma Hayfever Allergic rhinitis Food allergies
5
Q
What is the leading theory for the origin of allergies?
A
The skin sensitisation theory
6
Q
What is the skin sensitisation theory?
A
That there is a break in an infants skin (from eczema or infection) that allows allergens to cross the skin and react with the immune system. If there is then consequent lack of exposure to the allergen in the GI tract, it causes the immune system to become sensitised to the antigen.
7
Q
What is Type 1 hypersensitivity?
A
Antibodies trigger mast cells and basophils to release histamines and cytokines, leading to immediate reaction
8
Q
What kind of allergy is type 1 hypersensitivity?
A
Food allergy
9
Q
What is the normal presentation of a type 1 hypersensitivity reaction?
A
Acute itching, facial swelling, urticaria
10
Q
What antibodies are involved in a type 1 reaction?
A
IgE
11
Q
What happens in a type 2 hypersensitivity reaction?
A
Antibodies react to an allergen and activate the complement system, leading to direct damage to local cells (cytotoxic)
12
Q
What antibodies are involved in type 2 hypersensitivity reactions?
A
IgG and IgM
13
Q
What are some examples of type 2 hypersensitivity reactions?
A
Haemolytic disease of the newborn
Transfusion reactions
14
Q
What happens in Type 3 hypersensitivity reactions?
A
Immune complexes accumulate and cause damage to local tissues
15
Q
What are some examples of type 3 hypersensitivity reactions?
A
SLE
Rheumatoid arthritis
HSP
16
Q
What happens in type 4 hypersensitivity reactions?
A
Cell mediated hypersensitivity reactions caused by T-cells being inappropriately activated, causing inflammation and damage to local tissues
17
Q
What are some examples of type 4 hypersensitivity reactions?
A
Organ transplant rejection
Contact dermatitis
18
Q
What acronym helps remember hypersensitivity reactions?
A
ACID: Anaphylaxis Cytotoxic Immune complex Delayed type
19
Q
How are allergies usually diagnosed?
A
Detailed history
20
Q
What are the 3 main ways to test for allergy?
A
Skin prick testing
RAST testing
Food challenge testing
21
Q
Why are skin prick and RAST test unreliable and misleading?
A
They test for sensitisation and not allergy
22
Q
What is RAST testing?
A
Blood tests for total and specific IgE
23
Q
Why should you be cautious when performing an allergy test?
A
Often come back showing patient is sensitised to many things you have tested for, but they don’t necessarily need to avoid these things
24
Q
What is the gold standard test for diagnosing allergy?
A
Food challenge testing
25
How is skin prick testing performed?
Drops of different allergen solutions are applied to a patch of skin, along with a water and histamine control. After 15 minutest the size of the wheals of each allergens are assessed
26
What is patch testing?
Patch containing allergen is placed on skin. After 2-3 days the reaction is assessed
27
What allergies can patch testing help diagnose?
Allergic contact dermatitis (latex, perfumes, cosmetics or plants)
28
What happens during food challenge testing?
Child given increasing quantities of an allergen to assess reaction
29
How are allergies managed?
Avoid allergen
Prophylactic antihistamines
Epipen
30
How can you treat allergic reactions?
Antihistamines
Steroids
IM adrenaline for anaphylaxis
31
What is anaphylaxis?
Life threatening type-1 hypersensitivity reaction
32
What happens during anaphylaxis?
IgE stimulates mast cells to rapidly release histamine and other pro-inflammatories, causing rapid onset of symptoms
33
What is mast cell degranulation?
When mast cells rapidly release their contents (histamine and pro-inflammatory chemicals0
34
What are the key features that differentiate anaphylaxis from a non-anaphylactic allergic reaction?
Compromise of the airways, breathing or circulation
35
What symptoms may be present in anaphylaxis?
```
Urticaria
Itching
Andio-oedema (face swelling)
Abdominal pain
SOB
Wheeze
Larynx swelling
Tachycardia
Lightheadedness
Collapse
```
36
What is urticaria?
Hives- red, itchy welts
37
What are the principles of anaphylaxis management?
ABCDE
Im adrenaline
Antihistamines
Steroids
38
What should happen after an anaphylactic reaction and why?
Period of observation and assessment in cause a biphasic reaction occurs
39
How can anaphylaxis be confirmed retrospectively?
Measuring serum mast cell tryptase within 6 hours of the event
40
What are the indications for an adrenalin auto-injector?
All children and adolescents with anaphylactic reactions
May be given to those with generalised allergic reactions with specific risk factors: (steroid inhalers, poor access to medical treatment, nut or sting allergies, significant co-morbidities)
41
What kind of reaction is allergic rhinitis?
IgE-mediated type 1 hypersensitivity reaction
42
What happens in allergic rhinitis?
Environmental allergens cause allergic inflammatory response in nasal mucosa
43
What are the different types of allergic rhinitis?
Seasonal
Perennial
Occupational
44
What is an example of seasonal allergic rhinitis?
Hayfever
45
What is an example of perennial allergic rhinitis?
House dust mite allergy
46
What are the symptoms of allergic rhinitis?
Runny, blocked and itchy nose
Sneezing
Itchy, red, swollen eyes
47
What are the common triggers of allergic rhinitis?
```
Tree pollen
Grass
House dust mites
Pets
Mould
```
48
How is allergic rhinitis managed?
```
Avoid trigger:
Cleaning (hoovering, changing sheets regularly)
Stay inside during summer
Minimise contact with pets
Medications
```
49
What can be taken prior to exposure to reduce allergic symptoms?
Oral antihistamines
50
What are some examples of non-sedating antihistamines?
Cetirizine
Loratidine
Fexodenadine
51
What are some examples of sedating antihistamies?
Chlorphenamine
| Promethazine
52
What can be given to help allergic rhinitis?
Nasal corticosteroid sprays
| Nasal antihistamines
53
What age range is most typically affected by cow's milk protein allergy?
Infants and children under 3
54
What is cow's milk protein allergy?
Hypersensitivity to the protein in cow's milk
55
What are the two types of cow's milk protein allergy?
```
IgE mediated (rapid)
Non-IgE mediated (slower reaction time)
```
56
What is the difference between lactose intolerance and cows milk protein allergy?
Lactose is a sugar not a protein and intolerance is not an immune reaction
57
What are the risk factors for developing a cows milk protein allergy?
Formula fed
| Personal or family history of atopic conditions
58
When does cows milk protein allergy usually become apparent?
When babies are weaned from breast milk to formula milk or food containing milk
59
What are the common symptoms of cows milk protein allergy?
```
Bloating
Wind
Abdominal pain
Diarrhoea
Vomiting
Allergic symptoms (swelling, hives, cough, sneezing, eczema)
```
60
How is cows milk protein allergy diagnosed?
Full history
| Skin prick testing
61
How is cows milk protein allergy managed?
Avoid cows milk:
Breast feeding mothers avoid dairy products
Replace formula with hydrolysed formulas
62
What are hydrolysed formulas?
Formulas that contain cow's milk but the proteins have been broken down to avoid an immune response
63
By what age do most children outgrow cow's milk protein allergy?
3
64
How are children with cows milk protein allergy reintroduced to milk?
Milk ladder (slowly progress up ladder until they develop symptoms)
65
What is the difference between cow's milk intolerance and cow's milk allergy?
Cow's milk intolerance has same GI symptoms but no allergic features
66
Up to how may respiratory infections is it normal for a healthy child to have per year?
4-8
67
What associated features would cause you to initiate further assessment in a child with recurrent infections?
Chronic diarrhoea
Failure to thrive
Appearing unusually well with severe infection
Significantly more infections than expected
Unusual or persistent infections
68
What investigations may be done into recurrent infections in children?
```
FBC
Immunoglobulins
Complement proteins
Antibody responses
HIV test
CXR
Sweat test
CT chest
```
69
What is SCID?
Severe combined immunodeficiency
70
What causes SCID?
Genetic disorders that result in absent or dysfunctioning T and B cells
71
How will SCID present?
```
Persistent severe diarrhoea
Failure to thrive
Opportunistic infections
Unwell after live vaccines
Omenn syndrome
```
72
What is the most common cause of SCID?
Mutations in common gamma chain on X chromosome that codes for interleukin receptors on T & B cells.
73
What is the inheritance pattern of the most common cause of SCID?
X-linked recessive
74
What is Omenn syndrome?
Rare cause of SCID caused by mutation in RAG gene that codes for proteins in T & B cells
75
What is the inheritance pattern of Omenn syndrome?
Autosomal recessive
76
What causes the symptoms in Omenn syndrome?
Abnormally functioning and deregulated T cells that attack the tissues in the fetus or neonate
77
What are the classic symptoms of Omenn syndrome?
```
Erythroderma (rash)
Alopecia
Diarrhoea
Failure to thrive
Lymphadenopathy
Hepatosplenomegaly
```
78
How is SCID managed?
```
Specialist immunology centre
Treat underlying infections
Immunoglobulin therapy
Sterile environment
Haematopoietic stem cell transplantation
```
79
What is the action of B cells?
Produce antibodies
80
What is hypogammaglobulinemia?
Deficiency in immunoglobulins caused by abnormal B cells
81
What does hypogammaglobulinemia lead to?
Susceptibility to recurrent infections
82
What is the most common immunoglobulin deficiency?
Selective IgA deficiency
83
Where is IgA present?
Secretions of mucous membranes (saliva, resp/GI tract secretions, tears, sweat)
84
What does IgA protect against?
Opportunistic infections
85
How does IgA deficiency usually present?
Often asymptomatic
| Recurrent mucous membrane infections
86
When is IgA deficiency commonly tested for?
When testing for coeliac disease (anti-TTG and anti-EMA are IgA antibodies)
87
What is common variable immunodeficiency?
IgG and IgA +/- IgM deficiency
88
What causes common variable immunodeficiency?
Genetic mutation in genes coding for components of B cells
89
What does common variable immunodeficiency lead to?
Recurrent respiratory tract infections, leading to chronic lung disease
90
What are patients with common variable immunodeficiency more prone to?
Infections
Immune disorders (RA)
Cancers (Non-hodgkins lymphoma)
91
How is common variable immunodeficiency managed?
Regular immunoglobulin infusions
| Treat infections as they occur
92
What is X-linked agammaglobulinaemia?
X-linked recessive condition that results in abnormal B cell development and deficiency in all classes of immunoglobulins
93
What are some different T cell disorders?
```
DiGeorge syndrome
Purine nucleoside phosphorlyase deficiency
Wiskott-Aldrich syndrome
Ataxic telangiectasia
Acquired immunodeficiency syndrome
```
94
What causes DiGeorge syndrome?
Microdeletion in a portion of chromosome 22, leading to developmenal defect in third pharyngeal pouch and third brachial cleft
95
What is the main complication of DiGeorge syndrome?
Leads to underdeveloped thymus gland that is unable to make functional T cells
96
What are the key features of DiGeorge syndrome?
```
CATCH-22:
Congenital heart disease
Abnormal facial features
Thymus gland underdevelopment
Cleft palate
Hypoparathyroidism + Hypocalcaemia
22nd chromosome affected
```
97
What is Purine nucleoside phosphorylase deficiency?
Autosomal recessive condition that causes reduction in enzyme that protects against T-cell breakdown
98
What is PNPase?
Enzyme that helps breakdown purines
99
What builds up without the presence of PNPase?
dGTP metabolite
100
What cells is dGTP toxic to?
Exclusively T cells
101
What is WAS?
Wiskott-Aldrich syndrome
102
What kind of genetic inheritance is Wiskott-Aldrich syndrome?
X-linked recessive
103
What are the features of Wiskott-Aldrich syndrome?
```
Abnormal T cells
Thrombocyopenia
Immunodeficiency
Neutropenia
Eczema
Recurrent infections
Chronic bloody diarrhoea
```
104
What is ataxic telangiectasia?
Autosomal recessive condition affecting the gene that codes for a protein that plays an important part in DNA coding
105
What are the features of ataxic telangiectasia?
```
Low T-cells and immunoglobulins
Ataxia
Telangiectasia
Predisposition to cancers
Slow growth
Accelerated ageing
Liver failure
```
106
What causes acquired immunodeficiency syndrome?
HIV leading to reduced numbers of CD4 T-cells
107
What is the complement system most effective in dealing with?
Encapsulated organisms:
Haemophilus influenza B
Strep. pneumonia
Niesseria meningitidis
108
What do complement deficiencies make children particularly susceptible to?
Infections of the respiratory tract, ears and throat
109
What are complement deficiencies associated with?
Immune complex disorders (SLE)--> incomplete complement cascade leads to immune complexes building up and being deposited in tissues, leading to chronic inflammation
110
What is the most common complement deficiency?
C2 deficiency
111
What is a very important management step in patients with complement disorders?
Vaccinate against encapsulated organisms
112
What is the action of Bradykinin?
Responsible for promoting blood vessel dilation and increased vascular permeability in the inflammatory response
113
What does bradykinin cause?
Angioedema (swelling underneath skin)
114
What is the action of C1 esterase?
Inhibits bradykinin
115
What does an absence of C1 esterase cause?
Intermittent angioedema in response to minor triggers
116
Where does angioedema most commonly occur?
Lips and face but can occur anywhere, including the resp and GI tract
117
What are the complications of angioedema?
May last several days
| Can occur in he larynx and compromise the airway
118
What is Hereditary angioedema?
C1 Esterase inhibitor deficiency--> condition causing excess bradykinin leading to angioedema
119
How are patients with C1 esterase inhibitor deficiency treated?
IV C1-esterase inhibitor
120
How is hereditary angioedema tested for?
Check levels of C4, will be low in this condition
121
What does mannose-binding lectin deficiency lead to?
Inhibition of the alternative pathway of the complement system
122
What is the complication of mannose-binding lectin insufficiency?
In patients who are susceptible to infection, can lead to a more severe disease
