Hypersensitivity

Question 1

What is hypersensitivity?

Answer 1

Inappropriate immune response to otherwise harmless extrinsic antigens

Question 2

How does autoimmunity differ to hypersensitivity?

Answer 2

Autoimmunity is an inappropriate response to other wise tolerated intrinsic antigens
Hypersensitivity has a Type I antibody reaction aswell

Question 3

End result of inappropriate immune response?

Answer 3

Inflammation and destruction of tissue

Question 4

What mediates type I (immediate) antibody reaction?

Answer 4

IgE

Question 5

How does IgE become sensitised to an allergen?

Answer 5

Enzyme able to cleave occludin (forms tight junctions) in susceptible individual enters the mucosa
Taken up by APC, activates Th2 = actives IgE isotype switching, and binds mast cells and causes degranulation

Question 6

How does IgE cause degranulation of mast cells?

Answer 6

Upon repeated infection IgE cross linked = release of pro inflammatory cytokine (histamine, TNF alpha)

Question 7

Consequences of type I reaction?

Answer 7

Hives, asthma, eczema, anaphylaxis

Question 8

Systemic anaphylaxis

Answer 8

Allergens into BS and activate mast cells throughout the body e.g. heart, respiratory tract

Question 9

Physiological function of IgE

Answer 9

Rid body of parasites by physical force

Question 10

Why are normal effector functions inadequate for most parasites?

Answer 10

To big to be phagocytosed etc

Question 11

What type of T cells cause release of IgE?

Answer 11

Th2 (makes B cells switch to IgE)

Question 12

Other than degranulation and inflammation what is the function of mast cells at mucosal surfaces?

Answer 12

Sense PAMPs = activate innate

Question 13

3 causes of type II reaction in haemolytic anaemia

Answer 13

Autoimmunity (anti-erythrocyte autoantibodies)
Allergy to incompatible blood groups
Penicillin allergy

Question 14

Type III reaction?

Consequence?

Answer 14

Immune complex invade tissues and causes inflammation and destruction
Serum sickness in response to drugs e.g. penicillin

Question 15

How does penicillin cause hypersensitivity?

Answer 15

Modifies the protein on erythrocytes so body doesn’t recognise them as self

Question 16

Name the type I, II, III responses penicillin can cause?

Answer 16

I = Anaphylaxis
II = Haemolytic anaemia
III = Serum sickness

Question 17

How is the type IV (delayed) response visible? Cause

Answer 17

Localised acute inflammation (blisters) due to increased APC activation so more Th1 is activated relaxing cytokines and recruiting macrophages

Question 18

What antibody mediates this? What T cell?

Answer 18

IgG, Th1

Question 19

How can hay fever cause problems in dental practice?

Answer 19

Mouth breather = mild gingival hyperplasia

Anti-histamiens, xerostomia

Question 20

What is angioedema?

Answer 20

Rapid swelling of dermis and mucosa in response to allergen

Question 21

Why is type I reaction increasing?

Answer 21

Hygiene hypothesis (less exposure to potential allergens at young age = can’t build tolerance)