Type1Hpersensitivity

Question 1

Roles of IgG in helminth immunity

Answer 1

Roles of IgG in helminth immunity IgG: 
binds (coats) the worm or its ova → activates complement → C3a and C5a attracts neutrophils → neutrophils arrive and seize opsonized worm with their IgG and C3 receptors → Neutrophils lack helminthocidal mechanism → IgE to the rescue!

Question 2

Roles of IgE in helminth immunity

Answer 2

worms shed antigens → diffuse to nearby mast cell → FCeR of mast cells become loaded with anti-helminth IgE → worms antigen cross links the IgE → mast cells degranulate → release Histamine → cause gut smooth muscle contraction → peristalsis expels worms

Question 3

Roles of M2 in helminth immunity

Answer 3

Th2 finds helminth antigens presented by APC → secretes IL-4, IL-5, IL-13 → attracts M2 macrophages → heal damage and wall off M1-resistant helminthes

Question 4

Roles of Eosinophils in helminth immunity

Answer 4

have Fc receptor for IgG (which Is coating worm) → binds to opsonized worm → release granules containing Major Basic Protein (MBP) → toxic to helminths

• Eosinophils are also attracted by Th2

Question 5

What does eosiniphilia in the blood/sputum a sign of?

Answer 5

sign of parasitic disease or severe Type I immunopathology

Question 6

What are attracted by Th2 when it comes to helmith immunity?

Answer 6

M2 macrophages (by way of IL-4, 5 and 13)

Eosinophils

Question 7

Atopic

Answer 7

Atopy, atopic disease, and allergy are all synonymous and means “prone to develop any of the range of allergic syndromes” - Not helpful I know.

Question 8

Immediate hypersensitivity

Answer 8

Person has already made IgE

Question 9

Allergy

Answer 9

an atypical immune response to environmental antigens, eventually becoming characterized by increased reactivity of the end-organs to inflammatory mediators and irritants.

○ hypersensitivity disorder of the immune system.

○ Roughly same thing as atopy

Question 10

approximate incidence of atopic diseases in the general population, and in individuals with allergic parents.

Answer 10

○ ~20% of all people have it
35% ↑er risk with 1 allergic parent 

65% ↑er risk with 2 allergic parents

Question 11

mechanism of IgE-mediated hypersensitivity: 
Immediate reaction

Answer 11

1. IgE binds strongly to FCeR receptors on surface of mast cells (basophil IgE receptor) →
   
2. When 2 adjacent IgE molecules bind to mast cells and become cross-linked by allergen→
   
3. Mast cells release granules (containing histamine, heparin, enzymes, and TNF) → rapid action

Question 12

mechanism of IgE-mediated hypersensitivity: 
Late-Phase reaction

Answer 12

1. Activated Mast cell also initates series of enzymatic steps: 

   a. Phospholipase A (PLA2) cleaves arachidonic acid (aa) from membrane phospholipid → aa is converted via COX-pathway to prostaglandins or via Lipoxygenase to leukotrienes →prostaglandins and leukotrienes Initate inflammation and bronchoconstriction
   
i. Prostaglandins and leukotrienes that are initiated by mast cells are activated compounds. Together are called “eosinophil chemotactic factor of anaphylaxis” (ECF-A) → Really really good at attracting eosinophils in large numbers
2. Mast cells release cytokines also I guess . . . (he threw that little factoid in as an after thought)

Question 13

How to treat:


IgE-mediated hypersensitivity (Immediate reaction)

Answer 13

use antihistamines (receptor antagonists). Done son!

Question 14

How to treat:


IgE-mediated hypersensitivity (Late-Phase reaction)

Answer 14

. To treat the late-phase rxn, use B-adrenergic agonists

- can’t use antihistamines since it depends on prostaglandins, leuktotrienes and cytokines. Darn.

Question 15

What does Histamine do?

Answer 15

Histamine results in: 

local/systemic vasodilation,

increased permeability, 

gut and bronchial smooth muscle contraction

Question 16

Why do we lump atopic diseases together?

Answer 16

Cross-reactions are common in atopic disease.
○
For example, a person with T cellmediated contact dermatitis to latex (gloves, catheters, condoms) may have symptoms of IgE-mediated oral allergy to avocados, bananas, or chestnuts, all of which contain a cross-reactive antigen.

Question 17

Asthma definition

Answer 17

reversible bronchoconstrictive disease with progressive inflammation leading to fibrosis.

Question 18

reasons for using glucocorticoids in asthma treatment.

Answer 18

○ Risky w/ side effects w/ chronic use, but good in that they:

- Inhibit production of arachadonic acid from phospholipids → block PG and LT synthesis (late phase reaction)

- Induce apoptosis in eosinophils (remember Late-phase reactions attract a ton of them)