Greg - Clinical Immunology (Allergy) Flashcards
What are the clinical areas in the immunology lab?
(3)
Autoimmunity
Primary/secondary immunodeficiency
Allergy
What is done in an autoimmunity lab?
Screening for autoantibodies which are indicators for disease
Give an example of some antibodies measured in an autoimmunity lab
(5)
Antinuclear antibodies
Anti-neutrophil cytoplasmic antibodies
tTG antibodies
Rheumatoid factor
Anti-cyclic citrullinated peptide antibodies
List some methods of detecting antibodies in the autoimmunity lab
(3)
ELISA/immunoassay
Indirect immunofluorescence
Direct immunofluorescence
What is done in a primary/secondary immunodeficiency laboratory
Detecting dysfunction in the immune system caused by inherited (primary) or non-inherited (secondary) immunodeficiency
What methods are used in an immunodeficiency laboratory?
Flow cytometry
Cell function assays
Complement assays
Serum protein electrophoresis
What is carried out in an allergy laboratory?
Detecting allergies against environmental antigens
What methods are used in an allergy laboratory?
(3)
Specific IgE
Mast cell tryptase
Basophil activation
Why would we need to measure specific antibody responses?
To test for vaccination
To test for allergens
Why would we need to test for antinuclear antibodies
To test for lupus
What antibodies do we test for in coeliac disease?
Tissue transglutaminate antibodies (tTG antibodies)
What antibodies do we test for in lupus?
Antinuclear antibodies
What antibodies do we test for in rheumatoid arthritis?
Anti-cyclic citrullinated peptide antibodies
What is a primary immunodeficiency and give an example?
An inherited condition you are born with
e.g. X linked agammaglobulinaemia
What is a secondary immunodeficiency and give an example?
Immunodeficiency developed in life
e.g. HIV
What can we determine in an allergy lab?
Diagnosis and prognosis of an allergy
How severe your allergy will be and what causes the allergy
What is an allergy?
An inappropriate immune response to a harmless environmental antigen
List the components that are mainly involved in allergy
(5)
Mast cells
T cells
B cells
IgE
Histamine
What are the differences between an allergy and an intollerance?
Allergies are rapid onset, reproductible reactions
Intolerances are usually slower in onset and are not life-threatening
List the main symptoms of allergies
(6)
Asthma
Eczema
Rhinoconjunctivitis
Urticaria
Vomiting/diarrhoea
Systemic anaphylaxis/Death
What test is usually carried out within 6 hours after an allergic reaction?
Test for mast cell tryptase
Which detects products of mast cell degranulation
What are the requirements of a type 1 hypersensitivity?
(4)
Requires sensitisation
Multiple genetic factors contribute
Environmental factors contribute
Risk is conferred by many genes including HLA and cytokines
What usually happens to IgE after a while?
It degrades
What happens to IgE when it binds to mast cells?
IgE doesn’t break down and can remain stable
What happens when IgE bound to mast cells become cross linked?
It results in histamine being released (mast cell degranulation) and thus an allergy
What are the two mechanisms of diagnosing an allergy?
Measurement of IgE
Measurement of mast cell products such as tryptase
How is total IgE measured?
By immunoassay via chemiluminescence or fluorescence based means
Why is high IgE regarded as non specific?
(3)
It doesnt just indicate allergy
Indicates parasitic diseases
Or conditions such as hyper-IgE syndrome
What is a specific IgE test?
Measurement of the level of IgE directed against the suspected allergen
What is ELISA?
Enzyme-linked immunosorbent assay
A method which utilises the specificity of antibodies to quantify the level of a soluble analyte of interest
How is ELISA usually carried out?
(2)
Over multi-well plates or tubes (immunocap)
A labelled commercially available antibody is used to detect the molecule of interest
What are the three different types of reporter molecules?
Colorimetric
Chemiluminescence
Fluorescence
Whats the difference between an indirect and a direct ELISA?
Indirect -> antigen coats well, serum sample added, if antibodies present they bind to antigen, labelled antibody is added, amount of fluorescence is labelled
Direct -> labelled antibody binds to antigen
How do we use ELISA?
A series of standards with known concentration of antibody come with the bought in labelled antibody are run alongside the unknowns
Form standard curve
Measure sample against curve
How do you detect allergen specific IgE using an immunocap?
(7)
Antigen is pre-coated on a ‘cap’
Diluted patient serum is added and if the specific IgE is present will bind
Unbound serum proteins are washed away
A fluorescent-labelled secondary anti-IgE is added
Unbound secondary antibody is washed away
Fluorescence signal is measured
Fluorescence is proportional to anti-peanut antibody concentration
