10 - Allergy

Question 1

Types of hypersensitivity

Answer 1

Slide 6 of lecture

Question 2

Type II - cytotoxic rxn: immunopathogensis

Answer 2

IgG/M Ab response against combined self-foreign antigen at cell surface –> complement activation + phagocytosis/ADCC

Question 3

Type II - cytotoxic rxn: clinical features

Answer 3

Onset = minutes to hours

Cell lysis and necrosis

Question 4

Type II - cytotoxic rxn: common antigen

Answer 4

Penicillin

Question 5

Type II - cytotoxic rxn: Associated diseases

Answer 5

Erythroblastosis fetalis

Goodpasture’s nephritis

Question 6

Type III - immune complex rxn: immunopathology

Answer 6

IgG/M Ab against soluble antigen ==> complex deposition

Question 7

Type III - immune complex rxn: clinical features

Answer 7

Onset: 3-8 hours

Vasculitis

Question 8

Type III - immune complex rxn: cause

Answer 8

Serum sickness

Question 9

Type III - immune complex rxn: associated disease

Answer 9

SLE

Question 10

Type IV - delayed rxn: immunopathology

Answer 10

Antigen specific T-cell mediated cytotoxicity

Question 11

Type IV - delayed rxn: clinical features

Answer 11

Delayed onset 48-72 hours

Erythema induration

Question 12

Type IV - delayed rxn: common antigen

Answer 12

Metal e.g. nickel

Tuberculin rxn

Question 13

Type IV - delayed rxn: associated disease

Answer 13

Contact dermatitis

Question 14

Immune responses to parasitic disease inc…

Answer 14

Increased [IgE] - specific to antigen + cross-reactive

Tissue inflammation with eosinophilia&mastocytosis. Also basophil infiltration

Presence of CD4+ T cells secreting: IL4, IL5 and IL13

Question 15

What is the hygiene hypothesis?

Answer 15

Stimulation by microbes is protective. Epidemiological data shows increase in allergy.
Increased atopy (asthma) after anti-parasitic Rx
Prevention of autoimmunity (Crohn’s) by infections
Pro-biotics in pregnant women
Mechanism - Th1 Th2 deviation

Question 16

Immune response for allergens:

Answer 16

Antigens that initiate an IgE-mediated response

First encounter results in innate and IgM response

Question 17

How is IgE made?

Answer 17

B cell stimulated by IL4 + Th2 cell
This B cell proliferates
The pathogen binds to B cell and produces IgE

Question 18

Type I allergic response process

Answer 18

1. Allergen binds to CD4 and IL-4 is released.
2. B cells produce memory cells and plasma cell.
3. Plasma cell makes IgE
4. IgE binds to Fc receptor on sensitised mast cell
5. Vasoactive amines are released

Question 19

IgE mediated allergic response: immunopathogensis

Answer 19

IgE Ab mediated mast cell and basophil degranulation –> release of preformed and de novo synthesised inflammatory mediators

Question 20

IgE mediated allergic response: clinical features

Answer 20

Fast onset (15-30 mins)
Wheal and flare

Question 21

IgE mediated allergic response: late phase response

Answer 21

Eosinophils

Central role for Th2 T cell

Question 22

What is the role of the Th2?

Answer 22

Multiple cytokine release
Innate inflammatory response
Drive for Ig production

Question 23

What is the atopic triad?

Answer 23

Asthma, rhinitis, eczema

Question 24

What is anaphylaxis?

Answer 24

An acute, potentially life-threatening, IgE mediated systemic hypersensitivity response

Question 25

What makes a diagnosis of anaphylaxis?

Answer 25

History
Specific IgE (>0.35 KuA/L)
Skin prick test (>3mm wheal)
Intra-dermal test
Oral challenge test (gold standard)
Basophil activation test
Component resolved diagnostics

Question 26

Symptomatic treatment for anaphylaxis

Answer 26

Antihistamines
Steroids
AD

Can do immunotherapy via sub cut or sublingual

Question 27

Adverse rxns to food

Answer 27

GI - vomiting, diarrhoea, oral symptoms
Resp - rhinitis, bronchospasm
Cutaneous - urticaria, angioedema
Anaphylaxis