Lecture 12: Allergic Disease

Question 1

What are allergic diseases?

Answer 1

Immune reactions to a non-pathogen associated antigen and is a memory response

Question 2

What are the 4 types of allergic disease?

Answer 2

1. IgE mediated against extracellular antigen 2. IgG mediated cell antigen 3. IgG mediated against soluble antigens e.g. complement fixation 4. Th2 cell mediated against extracellular antigen

Question 3

What are the symptoms of an allergy?

Answer 3

Tears, swelling, rash, vomiting, sneezing, wheezing

Question 4

How are allergic responses initiated to an allergen?

Answer 4

Uptake and processing of allergen by APC onto MHC II then presentation to CD4 T cells

Question 5

What type of allergy is immediate and what type is delayed?

Answer 5

Type 1- immediate, Type 4- delayed (delayed type hypersensitivity reaction)

Question 6

What cells & molecules are involved in a type 1 hypersensitivity reaction?

Answer 6

Activation of T cell by APC induces it to become a Th2 cell. This produces IL-13, IL-4 and IL-5 which favours production of IgE by B cells

Question 7

What causes the symptoms of a Type 1 reaction?

Answer 7

Allergen bound IgE binding to Fc receptors on mast cells causing them to degranulate

Question 8

What is the effect of mast cell granules being released?

Answer 8

Increased fluid secretion and peristalsis in the GI tract, contraction of airways and increased mucous secretion, increased blood flow and permeability of blood vessels causing swelling

Question 9

Give 2 examples of mediators released by mast cells

Answer 9

Histamine and prostoglandins

Question 10

What causes anaphylactic shock?

Answer 10

Allergens in the blood stream either food ingested and absorbed, or through the skin

Question 11

What is the treatment for anaphylactic shock and how does it work?

Answer 11

Adrenaline from an epi-pen. Acts on alpha- and beta-adrenergic receptors to decrease vasodilation, relax smooth muscle, increase cardiac output

Question 12

How are different allergies diagnosed?

Answer 12

Skin prick test to detect allergen specific IgE- Allergen place on skin as a drop and skin is pricked through drop. Challenge test- elimination and reintroduction of foods from diet. Skin patch test to test cell mediated response- allergen discs taped to back then checked for redness/ swelling.

Question 13

What are possible treatments for allergies?

Answer 13

Prevention e.g. avoidance, vaccines. Treatment e.g. anti-inflammatory drugs, desensitisation