Lecture 4 - immunopathology + hypersensitivity

Question 1

what is allergy?

Answer 1

a reaction produced by the normal immune system (directed against innocuous antigens) in a pre-sensitised (immune) host

Question 2

innocuous antigen

Answer 2

self tissue which the immune system recognises as foreign because it is overreacting

Question 3

dendritic cell

Answer 3

cell that engulfs and presents material in its environment

Question 4

T lymphocyte

Answer 4

engage and secrete chemicals

Question 5

B lymphocytes

Answer 5

make antibodies

Question 6

what type of antibody is involved in type 1 hypersensitivity?

Answer 6

IgE

Question 7

what is the immunopathogenesis of type 1 hypersensitivity?

Answer 7

• IgE medicated mast cell and basophil degranulation

- release of preformed and de novo inflammatory mediators

Question 8

what are the clinical features of type 1 hypersensitivity?

Answer 8

• fast onset

- weal and flare

Question 9

which cells are involved in the late phase response of type 1 hypersensitivity?

Answer 9

• Eosinophils

- Th2 T cell –> a coordinator in this reaction

Question 10

what is the primary response of type 1 hypersensitivity?

Answer 10

degranulation and releases:

• histamine
• proteases
• chemotactic factors

Question 11

what is the secondary/ late (lipid mediators) response of type 1 hypersensitivity?

Answer 11

release:

• prostaglandin
• leukotrienes

Question 12

what is released when IgE and receptor on mast cell cross link?

Answer 12

histamine, proteases, chemotactic factors by degranulation

cause symptoms of allergic reaction

Question 13

what are the effects of histamine?

Answer 13

• bronchoconstriction
• increasing permeability of capillaries = swelling + lower BP
• swelling and inflammation, throat esp.
• increase HR
• may have blood clots, -gastric acid secretion
• diarrhoea

Question 14

what are the 3 types of type 1 hypersensitivity?

Answer 14

1. mild–> runny nose, itch, skin symptoms
2. moderate
3. severe –> anaphylaxis

Question 15

anaphylaxis

Answer 15

an acute, potentially life-threatening, IgE medicated systemic hypersensitivity reaction
a medical emergency

Question 16

urticaria

Answer 16

hive like over the skin

Question 17

what are the symptoms of mild type 1 hypersensitivity?

Answer 17

• ichy eyes or nose
• cutaneous pruritus
• flushing
• urticaria
• oral tingling/pruritus
• abdo pain/naudea/vomiting
• runny nose, sneezing

Question 18

what are the symptoms of moderate-severe type 1 hypersensitivity?

Answer 18

Anaphylaxis symptoms: prfound systemic reactions

• diffuse uriticaria and angioedema
• severe abdominal pain
• vomiting diarrhoea
• hoarseness cough
• SOB
• wheezing and cyanosis - respiratory arrest
• hypotension
• dizziness , loss of consciousness
• low BP

Question 19

what is the first step in sensitisation reaction?

Answer 19

allergen presented to dendritic cells and presented to naive T cells

Question 20

what do T cells differentiate into in sensitisation reaction?

Answer 20

Th2 cells

Question 21

what do Th2 cells secrete in sensitisation reaction?

Answer 21

cytokines IL-4 and IL-13

Question 22

what is the function of IL-4 and IL-13?

Answer 22

act as signal to naive B cells

Question 23

what do naive B cells differentiate into in sensitisation reaction?

Answer 23

memory B cells with specific IgE that will recognise the allergen on further exposure

Question 24

what is the change from B cell to memory cells called?

Answer 24

class switching because it moves from making IgM to IgE

Question 25

what are antibodies?

Answer 25

proteins with capability to cause allergic reactions

Question 26

what is the dual allergen exposure hypothesis?

Answer 26

This theory suggests that early cutaneous exposure to food protein through a disrupted skin barrier leads to allergic sensitisation.

Whereas early oral exposure to food allergen induces tolerance.

Question 27

how is an allergy diagnosed?

Answer 27

• patch test
• skin prick test ( > 3mm wheal)
• intra-dermal test
• oral challenge test (gold standard)
• component resolved diagnostics

Question 28

what is the atopic triad?

Answer 28

• asthma
• rhinitis
• eczema

Question 29

asthma

Answer 29

disease of inflammation and hyperactivity of the small airways

Question 30

which antigen causes the immediate symptoms of asthma?

Answer 30

IgE-mediated

Question 31

which type of hypersensitivity is atopic dermatitis?

Answer 31

type 4 hypersensitivity