When the immune system goes wrong (W24 and 25)

Question 1

Is autoimmunity the same as autoimmune disease?

Answer 1

No, autoimmunity (ie circulating autoreactive B and T cells) can be present without damge

Question 2

Type 1 hypersensitivity: Definition, cells/antibodies involved and example?

Answer 2

“Allergy”: Immediate hypersensitivity caused by innocuous antigens

Cells: Mast cells, eosinophils, IgE

Eg: peanut allergy

Question 3

Type 2 hypersensitivity: Definition, cells/antibodies involved and example?

Answer 3

Antibody dependent cytotoxicity

Cells: IgG, IgM

Acetylcholine receptors in Myasthenia Gravis, and TSH receptors in Grave’s Disease

Question 4

Type 3 hypersensitivity: Definition and example?

Answer 4

Immune complex mediated

Eg: SLE

Question 5

Type 4 hypersensitivity: Definition, cells/antibodies involved and example?

Answer 5

Delayed type hypersensitivity

Cells: T cells (CD4 Th1 cells), IL-2, IFN-gamma

Eg: T1DM, MS, Rheumatoid arthritic, Hashimoto’s Thyroiditis

Question 6

What is the likely presentation

vitals of someone in anaphylactic shock?

Answer 6

low BP
high HR
high RR
normal temp
inspiratory stridor, expiratory wheeze, urticarial rash, swollen nose and mouth.

Question 7

What is a basic mechanism for Type 1 hypersensitivity reactions?

Answer 7

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

Question 8

How do you treat anaphylaxis?

Answer 8

adrenaline= vasoconstriction
oxygen
SABA (eg salbutamol) to open airways

Question 9

Are there delayed effects in a Type 1 hypersensitivity reaction?

Answer 9

Yes: due to eosinophils that come in later, and synthesise lots of mediators over a long period.

Question 10

What is impetigo and what is it known as?

Answer 10

School sores, which arise secondary to scabies infestation–> scretch–> strep pyogenes and/or staph aureus

Question 11

Pansystolic murmur secondary to sore throat or impetigo in indigenous teen. What is the condition and organism?

Answer 11

Rheumatic heart disease. rheumatic fever (mitral stenosis)

Strep pyogenes

Question 12

Strep pyogenes: gram, catalase, growth on HBA and MAC, bacitraicin

Answer 12

gram+ cocci,
catalase-
beta haemolysis
no growth on Mac
Bacitraicin sensitive

Question 13

What is the Anti-streptolysin O test? (ASOT)

Answer 13

Test looks for antibodies to an S. pyogenes protein that lyses RBCs

Question 14

Pansystolic murmur secondary to sore throat or impetigo in indigenous teen. What other body symptoms might be affected?

Answer 14

Rheumatic fever–> may also cause arthralgia

Question 15

What is rheumatic fever?

Answer 15

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

Question 16

How does tolerance break down in rheumatic fever?

Answer 16

molecular mimicry: similarity between M protein and cadiac myosin

Question 17

Are there any organisms in the heart or joints with rheumatic fever?

Answer 17

No

Question 18

Can S. pyogenes be normal flora?

Answer 18

Yes

Question 19

How do you treat S pyogenes

Answer 19

Penicillin!

Question 20

What is the key differential diagnosis for Coeliac disease?

Answer 20

Giardia Lamblia

Question 21

What are the symptoms of Coeliac (8)?

Answer 21

weight loss, malaise, abdo pain, intermittent diarrhoea/ steatorrhoea, low BMI, mouth ulcers, anaemia, folate deficiency

Question 22

What are the biochemical tests for Coeliac?

Answer 22

anti-deaminated gliadin Abs (IgG and IgA), and anti-tissue transglutaminase antibodies (IgA)

Question 23

What does the jejunum of someone with coeliac look like? (3)

Answer 23

Blunted villi, elongated crypts, lymphocytic infiltrate

Question 24

What MHCs are associated with coeliac?

Answer 24

HLA DQ2 and HLA DQ8

Question 25

What is the pathogenesis of coeliac (briefly)?

Answer 25

Gluten ingested--> gliadin peptides--> gliadin deaminated by tgt--> deaminated gliadin binds to MHC--> CD4 T cell activation--> damage.

Question 26

What role to B cells/ antibodies play in coeliac pathogenesis?

Answer 26

They don't cause significant pathology, but are useful for testing.

Question 27

How do you definitively diagnose Coeliac?

Answer 27

Jejunal biopsy

Question 28

Besides GIT symptoms, what else might coeliac present as?

Answer 28

osteoporosis ulcers angular chelitis dermatitis hepatophormes

Question 29

What is the main serological screening test for SLE?

Answer 29

anti-nuclear antibody test

Question 30

Is SLE associated with high or low levels of C'?

Answer 30

LOW: C' may be used up in forming immune complexes, or lower due to liver disease.

Question 31

What kind of hypersensitivity is coeliac?

Answer 31

Type 4: T cell mediated

Question 32

What are 2 potential SLE triggers?

Answer 32

UV light (ie being in the sun) and EBV (glandular fever)

Question 33

Why would a urine dip stick be performed when testing for SLE?

Answer 33

often get Lupus Nephritis

Question 34

What are the clinical manifestations of SLE?

Answer 34

Complexes can deposit anywhere in the vasculature: nephritis, arthritis, shin rashes, hair follicles--> alopecia, brain, lungss

Question 35

Is detection of anti nuclear antibodies sufficient to diagnose SLE

Answer 35

No, low predictive value, it's only a screening test.

Question 36

What syndrome can Yersinia enterolitica cause?

Answer 36

Gastroenteritis. 5% of gastro in Aus.

Question 37

What is the gram stainof Y. enterolitica?

Answer 37

Gram- TINY rods

Question 38

What is CIN agar specific for?

Answer 38

Yersinia enterolitica

Question 39

What hypersensitivity syndrome can be caused by Y. enterolitica?

Answer 39

Rutter's syndrome: reactive arthritis that occurs 1-3 weeks post Y.. enterolitica gastro.

Question 40

What bacteria can cause Rutter's syndrome (reactive arthritis?)

Answer 40

Salmonella, Shigella. Campylobacter, Yersinia

Question 41

What syndromes can secondary reactive arthritis (Rutter's syndrome) follow?

Answer 41

Gastroenteritis or sometimes urethritis.

Question 42

What HLA is associates with reactive arthritis?

Answer 42

HLA B27

Question 43

Where is Y. enterolitica often aquired from

Answer 43

Dairy products from sheep, cows, goats that haven't been pasturised.

Question 44

What is the role if tissue trans glutaminase?

Answer 44

Deamidates free amino groups on particular glutamine residues on gliadin peptides Deamidation results in glutamine → glutamate which allows gliadin peptides to bind to HLA.

Question 45

What temperature does Y. enterolitica grow at?

Answer 45

25 degrees