11: Allergic diseases 🏁

Question 1

3 main risk factors for allergic diseases

Answer 1

• Enviroment
• Allergens
• Genetics

Question 2

In which type of allergic reaction is IgE the main reactant? Which type of antigens does IgE bind to?
How will IgE plasma cells and memory cells generated? What does IgE activate?
Name 3 examples of diseases.

Answer 2

Type 1 allergic reaction
- IgE binds to soluble antigens and activate mast cells
- e.g. Allergic rhinitis, asthma, systemic analphylaxis
- naive B cells can switch to IgE+ B cells with TH2 cell help (TCR+CD40), these cells can undergo differentiation into memory IgE B cells or bone marrow plasma cells in the germinal centre reaction

Question 3

Mast cells play a major role in type 1 allergic reactions. How?

Answer 3

Analphylactic reaction
antigen triggers IgE production, IgE binds to the surface of mast cells

next exposure to the same antigen results in binding of antigen (gridges between 2 antibodies), that results in degranulation of cell and release of histamine, histame increases the permeability and distension of blood capillaries.

Question 4

How are mast cells normally activated (3) and what is the function?

Answer 4

Activation
- Direct interaction of pathogen and TRLs+co receptor
- Fc-receptor mediated ativation
- compelement receptor mediated activation

Functions
- Wound healing via TFGß
- Immune cell recruitment/activation (eosinophil, B cell, Treg cell) via IL5/9/13
- Immune cell recruitment/activation of neutrophils via TNF
- neuroimmune interaction via Histamine, …
- Secretion and epithelial permeability via histamine, …
- coagulation and vascular permeability via histamine, …

Question 5

Which IL plays a major role in allergic condition regarding mast cells?

Answer 5

IL-4

Question 6

What is eosinophils trafficking?

Answer 6

Eosinophils trafficking refers to the movement or accumulation of eosinophils to specific tissues or organs in the body. Eosinophils are a key component of the immune system and play an important role in the body’s immune response

Functions are TH2 cell recruitment, activation of mast cells, macrophages, neutrophils, ….

Question 7

What is asthma?

Answer 7

A crhonic lung diseases marked by airway hyperresponsiveness and inflammation

results from inappropriate immune responsens (TH2-biased) to common alergens in genetically susceptible individuals like house dust mite enzymes, pollen, aspergillus fumigstus enzymes

Characteristics: infiltration of airway wall with mast cells, lymphocytes and eosinophils

Question 8

Clinical and biological diagnosis of asthma

Answer 8

clinical
- radiography and spirometry to test for fibrosis, smooth muscle thickening e.g.

biological
- count of eosinophils
- IgE detection
- topical allergen test

Question 9

Main difference between Asthma and COPD

Answer 9

Asthma
obstruction of airways (bronchii) is reversible, non allergic asthma possible, any age

COPD
obstruction of airways (small bronchii) is non-reversible, adults >45 years

Question 10

What is the main approach to explain lower levels of allergy prevalance in developing countries?

Answer 10

Hygiene hypothesis
In developing countries the interaction between enviroment and genes support an non-allergic state (TH1/TH2 regulation), e.g. due to:

low antibiotic use, high helminth burden, poor hygiene, rural homes in contrast to westerinzed countries

But there must be more factors leading to this difference (e.g. worse diagnostics)

Question 11

Name immune reactant, antigen, effectpr mechanism and examples of type 4 allergic diseases.

Answer 11

Type 4 allergic reactions are also known as delayed-type hypersensitivity reactions or cell-mediated hypersensitivity that occur within 24 to 72 hours after exposure to an soluable antigen.

Reaction to antigen presented on APCs, t cell recognize antigen and become activated, they migrate to site of infection, TH1 and TH2 response is possible

TH1 response: IFN-G, e.g contct dermatitis
TH2 response: IL4,IL-5, e.g. chronic asthma