Greg - Clinical Immunology (autoimmunity) Flashcards
What is an autoimmune reaction?
A reaction against self
The immune system targeting an autoantigen - self antigen
How many known autoimmune diseases are there?
There are 100+ diseases
Classify auto immune diseases
Organ-specific
Systemic
Give an example of an organ-specific autoimmune disease
Type 1 diabetes
Give an example of a systemic autoimmune disease
Systemic lupus erythematosus
Why are auto-immune conditions usually life long?
Because the antigen cannot be eradicated, stimulus is constant therefore disease is usually life-long
Give two occasions where the immune system must be suppressed?
Pregnancy
Transplant
In what case can an autoimmune condition be reversed?
(2)
If the autoimmune condition is diagnosed in childhood
The condition can burn out in puberty
What is an autoantigen?
(3)
An antigen of human
If an antigen is in organ e.g. pancreas it will only manifest locally
If antigen is in areas such as the joint it can be widespread
What is systemic disease?
A disease that can manifest anywhere in the body
e.g. systemic lupus erythematosus
Give two diseases that affect the nervous system
Multiple sclerosis
Myasthenia gravis
Give two diseases that affect the endocrine system
Type 1 diabetes mellitus
Grave’s disease
Give two diseases that affect the skin
Psoriasis
Dermatomyositis
Give two diseases that affect the GIT
Ulcerative colitis
Crohn’s Disease
Give two diseases that affect the bones
Reumatoid arthritis
Sjogren’s syndrome
Who do autoimmune disease affect most, males or females
Females
How does autoimmunity come about?
(3)
Initiated by a loss of tolerance
Autoreactive T cells should be deleted in the thymus -> in disease they are not -> out of the thymus they cause disease
Patients have some predisposing genetic background
Give an example of a mild disease
Psoriasis
Give an example of a fatal disease
Primary progressive MS
How can you have a predisposition to autoimmune conditions?
Mutations are found on the HLA region -> risk is transferred here
Having the gene does not mean you will have the disease but you will be at a very high risk
Give some things that can increase your risk of autoimmunity
Infections can increase the risk of autoimmunity
What is diabetes?
Loss of blood sugar control
How does insulin work in normal patients
- consumption of food is followed by insulin production
- insulin binds to insulin receptors on cells
- glucose transporters are moved to the cell surface
- available glucose is then taken into the cell
What happens in type 1 diabetes?
Insulin production is stopped
Autoimmune
What happens in type 2 diabetes?
Insulin resistance develops
Usually lifestyle-related
What is the main culprit in type 1 diabetes
The autoreactive T cell
What roll do autoreactive T cells have in type 1 diabetes
They lead the selective destruction of insulin-producing beta-cells
T cells made against antigens in the pancreas- against insulin - against GAD65 - against islet-cell antibodies
What roll do B cells have in type 1 diabetes
(3)
They produce anti-insulin antibodies
They produce anti-glutamic acid decarboxylase 65 (GAD65) antibodies
Anti-islet cell antibodies
What is GAD65
Glutamic acid decarboxylase 65
Why does the T cell attack the beta cells?
T cell acts like the B cell is infected with a virus
They only attack the Beta cells
Why can we not reverse diabetes at the moment
(2)
There is no stem cell for Beta cells
However Harvard has been able to make a stem cell into a beta cell -> which hopefully in the future can be put back into the body
What three methods are there to diagnosing autoimmune conditions?
The detection of antibodies
The detection of generic markers of inflammation - ESR and CRP
Measuring other generic marks of health - platelet levels and anaemia
What are two generic markers of inflammation?
ESR
CRP
What are two generic markers of health
Platelet levels
Anaemia (rbc count)
How do we detect autoantibodies by fluorescence?
Uses commercially available, labelled antibodies to detect patient autoantibodies in serum, or tissue
Give some examples of commercially available antibodies
(5)
Anti-nuclear antibodies
Anti-neutrophil cytoplasmic antibodies
Endomysial antibodies
Anti-glomerular basement membrane antibodies
Lupus skin
What is direct immunofluorescence
Detecting antibodies in human tissue samples
How do we carry out direct immunofluorescence?
(2)
We take a biopsy from a patient
Antibodies here are bound to antigen
Give an example of how we use direct immunofluorescence
Autoantibodies in the skin of lupus patients
What is indirect immunofluorescence?
Detecting antibodies from patient serum
How do we carry out indirect immunofluorescence
Antibodies are in serum
These react with antigen
There is a fluorescent reaction
Give an example of how we use indirect immunofluorescence
Used to detect antinuclear antibodies
How do we use direct immunofluorescence to detect systemic lupus erythematosus?
(4)
Patients with lupus may have antibodies deposited in their skin (butterfly rash) at the dermoepidermal junction
A skin biopsy is taken from the patient
Biopsy is sectioned and stained with anti-human IgM-FITC antibodies
Gives green fluorescence band -> ‘lupus band’
Where does lupus deposit autoantibodies?
At the dermoepidermal junction
What is used to stain for antibodies in lupus?
Anti human IgM FITC antibodies
What does a positive test for lupus look like|?
A positive test results in apple green fluorescence at the dermoepidermal junction
Explain how we use indirect immunofluorescence to detect anti-nuclear antibodies
Anti-nuclear antibodies are used to diagnose autoimmune connective tissue diseases such as rheumatoid arthritis and lupus
How are anti-nuclear antibodies produced
(3)
Company grows cells on slide
Hep2 cell line
These cells have a nice big nucleus so any reaction is easy to see
How are autoantibodies detected?
Via immunoassay e.g. ELISA
Immunocap
Why would ELISA be better than fluorescence detection of antibodies
ELISA is faster, automated and quantitative
How does immunocap work?
Each cap is coated with different antigens
Add diluted patient sample
Wash
Add conjugated antibody
What type of autoantibodies are used in ELISA?
They tend to be IgG/IgM/IgA in nature
How does immunocap assay work?
(7)
Autoantigen is pre-coated on a cap
Diluted patient serum is added and specific IgG if present will bind
Unbound serum proteins are washed away
A fluorescently-labelled secondary anti-IgG is added
Unbound secondary antibody is washed away
Fluorescence signal is measured
Fluorescence is proportional to anti-peanut antibody concentration
