When the immune system goes wrong (W24 and 25) Flashcards
Is autoimmunity the same as autoimmune disease?
No, autoimmunity (ie circulating autoreactive B and T cells) can be present without damge
Type 1 hypersensitivity: Definition, cells/antibodies involved and example?
“Allergy”: Immediate hypersensitivity caused by innocuous antigens
Cells: Mast cells, eosinophils, IgE
Eg: peanut allergy
Type 2 hypersensitivity: Definition, cells/antibodies involved and example?
Antibody dependent cytotoxicity
Cells: IgG, IgM
Acetylcholine receptors in Myasthenia Gravis, and TSH receptors in Grave’s Disease
Type 3 hypersensitivity: Definition and example?
Immune complex mediated
Eg: SLE
Type 4 hypersensitivity: Definition, cells/antibodies involved and example?
Delayed type hypersensitivity
Cells: T cells (CD4 Th1 cells), IL-2, IFN-gamma
Eg: T1DM, MS, Rheumatoid arthritic, Hashimoto’s Thyroiditis
What is the likely presentation
vitals of someone in anaphylactic shock?
low BP high HR high RR normal temp inspiratory stridor, expiratory wheeze, urticarial rash, swollen nose and mouth.
What is a basic mechanism for Type 1 hypersensitivity reactions?
1st encounter with allergen–> binds to APC–> Th2 response–> IL-4–> B cells–> IgE–> released and binds to (“primes”) mast cells–> mast cell distribute all over body.
2nd encounter: binding of allergen to IgE on mast cells–> degranulation–> histamine, leukotrienes, cytokines
How do you treat anaphylaxis?
adrenaline= vasoconstriction
oxygen
SABA (eg salbutamol) to open airways
Are there delayed effects in a Type 1 hypersensitivity reaction?
Yes: due to eosinophils that come in later, and synthesise lots of mediators over a long period.
What is impetigo and what is it known as?
School sores, which arise secondary to scabies infestation–> scretch–> strep pyogenes and/or staph aureus
Pansystolic murmur secondary to sore throat or impetigo in indigenous teen. What is the condition and organism?
Rheumatic heart disease. rheumatic fever (mitral stenosis)
Strep pyogenes
Strep pyogenes: gram, catalase, growth on HBA and MAC, bacitraicin
gram+ cocci, catalase- beta haemolysis no growth on Mac Bacitraicin sensitive
What is the Anti-streptolysin O test? (ASOT)
Test looks for antibodies to an S. pyogenes protein that lyses RBCs
Pansystolic murmur secondary to sore throat or impetigo in indigenous teen. What other body symptoms might be affected?
Rheumatic fever–> may also cause arthralgia
What is rheumatic fever?
Autoimmune disease that follows S. pyogenes infection–> antibodies to the M protein cross react with cardiac myosin–> cross link on mitral valve–> allows C’ fixation and further damage–> stenosis
How does tolerance break down in rheumatic fever?
molecular mimicry: similarity between M protein and cadiac myosin
Are there any organisms in the heart or joints with rheumatic fever?
No
Can S. pyogenes be normal flora?
Yes
How do you treat S pyogenes
Penicillin!
What is the key differential diagnosis for Coeliac disease?
Giardia Lamblia
What are the symptoms of Coeliac (8)?
weight loss, malaise, abdo pain, intermittent diarrhoea/ steatorrhoea, low BMI, mouth ulcers, anaemia, folate deficiency
What are the biochemical tests for Coeliac?
anti-deaminated gliadin Abs (IgG and IgA), and anti-tissue transglutaminase antibodies (IgA)
What does the jejunum of someone with coeliac look like? (3)
Blunted villi, elongated crypts, lymphocytic infiltrate
What MHCs are associated with coeliac?
HLA DQ2 and HLA DQ8
What is the pathogenesis of coeliac (briefly)?
Gluten ingested–> gliadin peptides–> gliadin deaminated by tgt–> deaminated gliadin binds to MHC–> CD4 T cell activation–> damage.
What role to B cells/ antibodies play in coeliac pathogenesis?
They don’t cause significant pathology, but are useful for testing.
How do you definitively diagnose Coeliac?
Jejunal biopsy
Besides GIT symptoms, what else might coeliac present as?
osteoporosis
ulcers
angular chelitis
dermatitis hepatophormes
What is the main serological screening test for SLE?
anti-nuclear antibody test
Is SLE associated with high or low levels of C’?
LOW: C’ may be used up in forming immune complexes, or lower due to liver disease.
What kind of hypersensitivity is coeliac?
Type 4: T cell mediated
What are 2 potential SLE triggers?
UV light (ie being in the sun) and EBV (glandular fever)
Why would a urine dip stick be performed when testing for SLE?
often get Lupus Nephritis
What are the clinical manifestations of SLE?
Complexes can deposit anywhere in the vasculature: nephritis, arthritis, shin rashes, hair follicles–> alopecia, brain, lungss
Is detection of anti nuclear antibodies sufficient to diagnose SLE
No, low predictive value, it’s only a screening test.
What syndrome can Yersinia enterolitica cause?
Gastroenteritis. 5% of gastro in Aus.
What is the gram stainof Y. enterolitica?
Gram- TINY rods
What is CIN agar specific for?
Yersinia enterolitica
What hypersensitivity syndrome can be caused by Y. enterolitica?
Rutter’s syndrome: reactive arthritis that occurs 1-3 weeks post Y.. enterolitica gastro.
What bacteria can cause Rutter’s syndrome (reactive arthritis?)
Salmonella, Shigella. Campylobacter, Yersinia
What syndromes can secondary reactive arthritis (Rutter’s syndrome) follow?
Gastroenteritis or sometimes urethritis.
What HLA is associates with reactive arthritis?
HLA B27
Where is Y. enterolitica often aquired from
Dairy products from sheep, cows, goats that haven’t been pasturised.
What is the role if tissue trans glutaminase?
Deamidates free amino groups on particular
glutamine residues on gliadin peptides
Deamidation results in glutamine → glutamate which allows gliadin peptides to bind to HLA.
What temperature does Y. enterolitica grow at?
25 degrees
