Block E Lecture 2: Allergies Flashcards
What is an allergy defined as?
Disease following a response by the immune system to an otherwise harmless antigen
(Slide 3)
What percentage of children and adults suffer from allergies?
40% of children and 30% of adults
(Slide 3)
What is the most common type of allergen?
Proteases
(Slide 5)
Are allergens soluble?
Yes, highly
(Slide 5)
Do allergens have intrinsic enzyme activity?
Yes - protease activity
(Slide 5)
What 2 things do allergens cleave and activate?
Complement components and an inactive form of IL-33 produced by epithelial cells
(Slide 5)
What do protease allergens disrupt?
The integrity of the endothelial barrier
(Slide 5)
What do protease allergens stimulate?
Protease receptors on immune cells
(Slide 5)
Do allergens contain PAMPS?
They can but don’t always
(Slide 5)
Are most airborne antigens big or small?
Small
(Slide 6)
What are most airborne allergens carried on?
Dry particles
(Slide 6)
What is an allergens first contact called?
Sensitisation
(Slide 7)
How does der p 1 enzyme cause allergy?
It cleaves occludin in tight junctions and enters mucosa, where it is taken up by dendritic cells for Th2 activation. The Th2 cell then induces B-cell antibody switch to IgE. Der p 1- specific IgE then binds to the FcεRI receptor on mast cell and then upon subsequent exposure to the same allergen (in this case Derp p 1) it binds to IgE already on the surface of immune cells, triggering mast-cell degranulation, causing allergic symptoms
(Slide 7)
What immune cells express the FcεRI receptor?
Mast cells, basophils and eosinophils (to a lesser extent)
(Slide 9)
When does cross linking occur?
Cross-linking occurs when the allergen binds simultaneously to the Fab (antigen-binding) regions of two or more IgE antibodies bound to adjacent FcεRI receptors
(Slide 9)
What 2 things happen when IgE is cross-linked to an antigen?
Expression of CD40L and release of IL-4
(Slide 9)
What do CD40L and IL-4 produced by IgE cross-linking signal?
For the B cells to produce more IgE
(Slide 9)
What are 2 things which normal degranulation cause and how do these help clear parasites?
Causes vasodilation
Increased vascular permeability
These result in an influx of immune and plasma mediators to the site of infection to attack the pathogen
(Slide 10)
How does degranulation harm the body in an allergic response?
Unnecessary increases in vascular permeability and inflammation leading to tissue damage with no benefit
(Slide 10)
What percent of mast cell granules does histamine account for?
10%
(Slide 11)
How long does histamine take to take effect?
Minutes
(Slide 11)
What receptor does histamine bind?
Histamine receptors (H1-4)
(Slide 11)
What are 4 examples of the effects of histamine?
Contraction of intestinal and bronchial smooth muscle
Increased permeability of veins
Increased mucus secretion
Increased stomach acid
(Slide 11)