Therapeutics and Immunology: Lecture 3: Allergy and hypersensitivity

Question 1

What is hypersensitivity

Answer 1

Classes of hypersensitivity defined by effector mechanism by which damage occurs due to outside antigen source

Question 2

Describe class 1 hypersensitivity

Answer 2

Most common

Effector mechanism:
IgE antibody on MAST cells

Example:
Hayfever, asthma, anaphylaxis

Question 3

Describe class 2 hypersensitivity

Answer 3

Effector mechanism:
IgM and IgG antibody mediated cell killing

Example:
Mismatched blood transfusion
Penicillin
Haemolytic anaemia of the new born

Question 4

Describe class 3 hypersensitivity

Answer 4

Effector mechanism:
IgG antibody immune complexes

Example:
Serum sickness
Long term mAb use

Question 5

Describe class 4 hypersensitivity

Answer 5

Effector mechanism:
T cells- triggering inflammation in response to microbial peptides

Example:
Contact Dermatitis

Question 6

What can class 1 hypersensitivity lead to symptom wise

Answer 6

Swelling
Sneezing
Itching
Swelling
Vasodilation

Question 7

What are the three main type 1 allergies and describe them

Answer 7

Hayfever: allergen (antigen) in upper respiratory tract and eyes
Itching and sneezing

Asthma:
Allergen (antigen) in lower respiratory tract
Air vessel constriction: shortness of breath, wheezing

Anaphylaxis:
Lots of mast cells triggered at one time
Large systemic vasodilation leads to catastrophic blood pressure loss and death

Question 8

What are typical external antigens that stimulate and sensitise individuals to IgE response

Answer 8

Pollen
Dust mites
Medicines
Food components and contaminants
Rodents, birds
Insect bites
Humans 
Work

Question 9

How do you normally detect what you are allergic to

Answer 9

remove antigen and skin prick test

Question 10

What are IgM and IgG roles

Answer 10

Killing pathogens

Activate a complement which can punch holes in cell walls

IgG: INACTIVATION OF TOXINS

Question 11

What occurs in drug induced haemolytic anaemia in type 2 hypersensitivity reactions

Answer 11

Antibodies bind to red blood cells to directly kill them which leads to anaemia

Question 12

What is serum sickness

Answer 12

High levels of antibody bound to foreign protein

Question 13

What is a monoclonal antibody and give an example

Answer 13

A single rearranged antibody is selected that binds to the desired antigen

Example: Human TNF and human HER2 receptor

Question 14

What is the role of monoclonal antibody

Answer 14

Developed to block signals, kill cells and activate receptors

Question 15

What is passive immunisation

Answer 15

the transfer of antibodies into the body

Question 16

What are the interventions for hypersensitivity and describe them

Answer 16

ONLY cure: AVOID ANTIGENS: dust mask for hay fever

Use of antihistamines and glucocorticoids- target antigen specific effector functions

Symptomatic relief: decongestants, Beta 2 adrenoceptor agonist inhalers, ephedrine pens

Question 17

Give some H1 receptor antagonists examples

Answer 17

Loratadine and cetirizine

Question 18

How do you manage the symptoms of a hypersensitivity reaction, state the examples

Answer 18

Ephedrine/adrenaline for anaphylaxis

Ephedrine autoinjectors- EpiPEN- compensates for massive blood pressure drop

Salbutamol for asthma- opens air ways