Hypersensitivity Rxns

Question 1

what is a hypersensitivity run and what do they require

Answer 1

Over rxn of the immune system to self or non self antigens

-require a sensitized host (prior exposure)

Question 2

What are type 1 hypersensitivities mediated by

Answer 2

IgE mediated

-soluble antigens cross link IgE antibodies bound to mast cels/basophils

Question 3

examples of type 1 hypersensitivites (4)

Answer 3

atopy
allergies
acute allergic asthma
anaphylaxis

Question 4

How are IgE antibodies developed : what cells stim them and ILs needed

Answer 4

B cells stimed by Th2 cells

need IL4,5,13

Question 5

Steps to get mast cells sensitized

Answer 5

1. APC present to Th2
   2.Th2 acctivate b cells
2. B cells proliferate into plasma cells and secrete IgE
   4 IgE bind to mast cells sensitizing them

Question 6

What does reexposure to antigens bind to

Answer 6

preexposure of certain antigens bind IgE and crosslink FceRI receptors

Question 7

What is released in the immediate type 1 hypersensitivity and what occurs (2)

Answer 7

immediately after exposure histamine and leukotriene released which causes: vasodilation of arterioles and increased permeability, airway smooth mm contraction, leukocyte extravasation to affected site

Question 8

When does late phase type 1 hypersensitivity occur and what is released

Answer 8

2-6 hrs post

-cytokines (IL4,5,13) amplifies type 1 rxn (activate eosinophils, neutrophils, monocytes etc)

Question 9

Natural hx of type 1 hypersensitivity

Answer 9

12hrs- 3days

acute rxn

Question 10

What percentage of people have atopy and why

Answer 10

10-20%

-higer total lvl of IgE in circulation, more eosinophils

Question 11

What is the clinical manifestation to atopy

Answer 11

allergy

Question 12

What leads to atopy

Answer 12

1. genetics (components of immune system)
2. Environment (infection)
3. Lifestyle (stress, obesity)

Question 13

What is allergy mediated by

Answer 13

IgE antibodies

Question 14

Effect of type 1 hypersensitivity on nasal passages and eyes

Answer 14

eyes: redness, itchy, watery eyes, conjunctiva
nasal: allergic rhinitis, sneezing, runny nose, coughing etc, respiratory distress etc

Question 15

What is asthma

Answer 15

disease of the bronchi and bronchioles causing attacks/paroxysms of reversible airflow obstruction (airway inflammation, bronchospasm, mucus hyper production)

Question 16

What are the primary clinical manifestations on the skin of type 1 hypersensitivities

Answer 16

1. dermatitis (eczema)- red area of superficial skin that is often itchy
2. Urticaria (hives)- raised areas surrounded by a red base, itchy, typically lasts <24hrs

Question 17

Food allergy vs food intolerance

Answer 17

allergy- IgE mediated process

intolerance- IgG mediated process

Question 18

What is anaphylazis and how is it mediated

Answer 18

IgE mediated- widespread basophil degranulation+ systemic inflammation
-itchy hives,dyspenia, light-headedness, low bp

Question 19

common characteristics of allegens (5)

Answer 19

• low molecular weight
• highly soluble
• multivalent antigens
• enzymatically active
• stable chem structue

Question 20

What is the major allergen of house dust mite and what does it do

Answer 20

Der p1

Break up tight junctions getting increased access to APCs in mucosal tissues

Question 21

Gold standard of allergy testing

Answer 21

blood testing: cells timed with antigen under investigation and IgE antibodies measured

Question 22

What are drugs to treat allergies

Answer 22

Antihistamines
Leukotriene inhibitors
Inhaled bronchodialators
Epinephrine- relaxes sm mm
Allergy shots- (expand tolergenic responses)

Question 23

What are type II hypersensitivities mediated by

Answer 23

IgG or IgM antibodies directed against cell associated antigens or ECM antigens

Question 24

What do type II hypersensitivities result in

Answer 24

Cytotoxic responeses

• activation of classic complement path
• antibody dependent cell mediated cytotoxicity
• Phagocytosis

Question 25

What are isoantibodies

Answer 25

IgM/IgG antibodies against blood antigens you don’t have

Question 26

What do isoantibodies do when blood is mismatched (3)

Answer 26

1. Agglutination 2. Clumps activate classical complement pathway 3. Hemolysis by MAC/inflammation/opsinization

Question 27

When does hemolytic disease of the fetus and newborn occur

Answer 27

if mother is rh- and child is rh+, mother may generate anti rh IgG antibodies and if next child is rh+ it will initiate hemolytic rxn

Question 28

what occurs in myasthenia gravis

Answer 28

type II hypersensitivity IgG autoantibodies target nicotinic act receptors on neuromuscular junction blocking action pot/ activate classical complement pathway

Question 29

What occurs in Graves disease

Answer 29

Type II hypersensitivity -autoimmune disorder where IgG antibodies bind to thyroid stem hormone receptor causing over prod of T3/T4 (hyperthyroidism)

Question 30

Symptoms of Graves disease

Answer 30

Unexplained weight loss, elevated HR, high BP, anxiety/irratability etc

Question 31

What are type III hypersensitivities and what do they activate

Answer 31

formation of small immune complexes between IgG antibodies and soluble antigens (deposits in walls of blood v) -activate classical complement pathway, inflammation

Question 32

What is arthur’s reaction and serum sickness due to and what do they do

Answer 32

type III hypersensitivity -small immune complexes in tissues causing inflammation/tissue damage Arthus- localized serum- systemic

Question 33

What is systemic lupus erythematosus and what causes it

Answer 33

Type III hypersensitivity (IgG autoantibodies and soluble nuclear antigens)-deposit in tissues and activate complement/inflammation -fatiue, fever, jt pain/swelling, rashes, any organ targeted

Question 34

What is required for a type 4 hypersensitivity and timeframe

Answer 34

- delayed hypersensitivity (>24hrs) | - Requires prior exposure to antigen and sensitization to generate antigen specific t cells

Question 35

What type of antigen specific t cell is required for TB type 4 hypersensitivity

Answer 35

Th1 cells

Question 36

What type of antigen specific t cell is required for chronic asthma and what does it cause

Answer 36

Th2 cells | -airway remodelling, hyperresponsitivness (to irritation) and obstruction

Question 37

What type of antigen specific t cells are required for poison ivy (type 4) and what do each do

Answer 37

th1 cells= activate macrophages clts- induce apoptosis