Hypersensitivity

Question 1

Type 1 hypersensitivity

Answer 1

allergies/atopic disorders, anaphylatic reactions depend on route of entry and location of responding cells, antigens activate TH2 which release IL-4 to stimulate IgE response which activates mast cells

2 phases: immediate (minutes) phase and late phase (hours) which involves cellular infiltration

Question 2

crosslinking of IgE

Answer 2

activate mast cells to release mediators (granles) such as histamine

Question 3

wheal and flare

Answer 3

part of the immediate response, swelling from leakage-histamine effect and engorged with RBCs

leads to late phase with more widespread swelling and inflammation

Question 4

serotonin

Answer 4

affects vascular permeability

Question 5

SRS-A

Answer 5

slow releasing substance of anaphylaxis, mixture of leukotrienes produced during response

Question 6

TNF

Answer 6

stimulates expression of adhesion molecules on endothelial cells

Question 7

basophils and eosinophils

Answer 7

only expresses IgE receptors after they become activated allowing them to bind IgE. Once activated, they degranulate and increase in number.

Question 8

response to subcutaneous allergen

Answer 8

ex. insect allergen, results in localized swelling, urticaria (hives), angiodema (deeper, diffuse swelling), eczema

used to test skin for allergies (RAST assay)

Question 9

responses to inhaled allergen

Answer 9

allergic rhinitis, results in the sensitization of mast cell and eosinophils producing mucus.

peptides derived from pollen grains are presented by APCs to activate antigen specific T cells which secrete IL-4 resulting in isotype switch to IgE.

Question 10

allergic asthma

Answer 10

can result in both an acute response and chronic response

for the acute response, mast cell capture antigen and inflammatory mediators contract smooth muscle, increase mucus secretion, and increase blood vessel permeability

Question 11

chronic asthma

Answer 11

can occur in the absence of allergen - persons with chronic asthma are hyper responsive to other irritants in the air such as cigarette smoke

cellular infiltrate and inflammation can lead to tissue remodeling.

Question 12

reaction to absorbed allergen

Answer 12

food allergies, ingestion of antigen activates mucosal mast cells, antigen diffuses into blood vells and can cause urticaria, vomiting, diarrhea. mechanism is similar to what body does to expel parasites.

Question 13

systemic allergen - systemic anaphylaxis

Answer 13

most severe form of Type 1 - antigens include drugs, serum, venom, peanuts

antigen in bloodstream enters tissues and activates connective mast cells throughout body

Question 14

hygiene hypothesis

Answer 14

poorer hygiene results in exposure to TH1 inducing infections which protect against allergy

Question 15

Counter Regulation Hypothesis

Answer 15

infections lead to production of IL-10 and TGF-beta which downregulate both TH1 and TH2 responses so less hypersensitivity

Question 16

treatment to Type 1 hypersensitivity

Answer 16

avoid allergen, treat symptoms, desensitization, allergenic peptide vaccination, anti-IgE, anti-cytokines

Question 17

Type 2 hypersensitivity

Answer 17

mediated by IgG, drug induced or blood transfusion, antibodies bind to cell associated antigen or cell surface receptor and fix complement, can lead to lysis of RBCs or platelets

Question 18

Type 3 hypersensitivity

Answer 18

formation of large latticed immune complexes leading to downstream cellular damage depending on what tissue site they deposit

can lead to arthus (localized) reaction or serum sickness

Question 19

serum sickness

Answer 19

formation of antigen:antibody complexes, occurs after development of antibody to antigen (7-10 days), may occur after large amounts of foreign protein in antisera, generally resolves itself

Question 20

Type 4 hypersensitivity

Answer 20

mediated by TH1 cells, reactions include delayed type hypersensitivity (TB test), contact hypersensitivity (poison ivy), celiac disease (gluten sensitive enteropathy)

Question 21

treatment for types 2, 3, 4 hypersensitivity

Answer 21

avoidance, anti-inflammatories, reduction of immune response (steroids), regulatory T cells (peptide vaccination), blocking of effector mechanisms