Chapter 11

Question 1

Type I (Immediate) Hypersensitivity

Answer 1

Release of mediators from the mast cells

Question 2

Type II Hypersensitivity

Answer 2

Mediated by antibodies

Question 3

Type III Hypersensitivity

Answer 3

Mediated by immune complexes

Question 4

Type IV Hypersensitivity

Answer 4

Mediated by T cells

Question 5

Immediate Hypersensitivity / AKA (Allergy or Atopy)

Answer 5

Reaction to certain antigens that is mediated by IgE antibody and mast cells

Question 6

Common types of these reactions

Answer 6

Hay fever, food allergies, bronchial asthma, & anaphylaxis

Question 7

1. Sequence of events in immediate hypersensitivity

Answer 7

Activation of TH2 cells and production of IgE antibodies

Question 8

Antigens that elicit immediate hypersensitivity (allergic) reactions are called

Answer 8

Allergens

Question 9

What does TH2 cells secrete

Answer 9

cytokines IL-4 and IL-13 and stimulate B lymphocytes specific for the foreign antigens to switch to IgE-producing plasma cells

Question 10

Individuals produce large amounts of IgE antibody in response to antigens that do not elicit IgE responses in other people.

Answer 10

Atopic

Question 11

Strong familial predisposition for Type 1 hypersensitivity reactions; this predisposition is genetically determined.

Answer 11

Atopy

Question 12

2. Sequence of events in immediate hypersensitivity

Answer 12

Activation of mast cells.

Question 13

Process of coating mast cells with IgE

Answer 13

Sensitization
Coating with IgE specific for an antigen makes mast cells sensitive to activation by a subsequent encounter with that antigen*

Question 14

Where are mast cells present?

Answer 14

In all connective tissues (esp. under epithelia), and these cells are usually located adjacent to blood vessels

Question 15

Route of allergen entry determines which mast cells are activated by cross-linking of allergen-specific IgE.

Answer 15

(i) inhaled allergens activate mast cells in submucosal tissues of bronchus; (ii) ingested allergens activate mast cells in wall of intestine.

Question 16

3. Sequence of events in immediate hypersensitivity

Answer 16

FcεRI, high-affinity receptor for IgE, consists of 3 polypeptides.

Question 17

Where does the one polypeptide bind?

Answer 17

Fc portion of ε heavy chain very strongly

Question 18

What are the other two chains of the receptor?

Answer 18

Signaling proteins.

Question 19

Mast cells are always?

Answer 19

Coated with IgE bound to FcεRI

Question 20

4. Sequence of events in immediate hypersensitivity

Answer 20

When mast cells sensitized by IgE are exposed to allergen, the cells are activated to secrete mediators.

Question 21

Signals lead to three types of responses in the mast cell

Answer 21

(i) rapid release of granule contents (degranulation), (ii) synthesis and secretion of lipid mediators, and (iii) synthesis and secretion of cytokines.

Question 22

Most important mediators produced by mast cells

Answer 22

vasoactive amines and proteases stored in and released from granules; secreted products of arachidonic acid metabolism; and cytokines

Question 23

causes dilation of small blood vessels; increases vascular permeability; stimulates transient contraction of smooth muscles.

Answer 23

Preformed vasoamines (e.g., histamine)

Question 24

damage local tissues.

Answer 24

Preformed proteases

Question 25

prostaglandins (cause vascular dilation) and leukotrienes (stimulate prolonged smooth muscle contraction).

Answer 25

Arachidonic acid metabolites

Question 26

induce local inflammation.

Answer 26

Cytokines

Question 27

produced by mast cells stimulate recruitment of leukocytes (cause late-phase reaction) – principal leukocytes involved are eosinophils, neutrophils, and TH2 cells

Answer 27

Cytokines

Question 28

liberate proteases that cause tissue damage

Answer 28

Eosinophils and neutrophils

Question 29

exacerbate reaction by producing more cytokines

Answer 29

TH2 cells

Question 30

infiltration of tissues with eosinophils, neutrophils, basophils, monocytes, and CD4+ T cells as well as tissue destruction, typically in the form of mucosal epithelial cell damage.

Answer 30

Histology

Question 31

Preformed mediators in secretory granules

Answer 31

Histamine & Lysosomal enzymes

Question 32

increase vascular permeability, smooth muscle contraction

Answer 32

Histamine

Question 33

breakdown extracellular matrix proteins; tissue damage

Answer 33

Lysosomal enzymes (chymotryptase, tryptase, and other proteases)

Question 34

Newly synthesized

Answer 34

Arachidonic acid metabolites, lipid mediators (leukotrienes & prostaglandins) & Cytokines

Question 35

IL-4 & IL-13 (promote TH2 differentiation and IgE production); TNF-α (promotes tissue inflammation)

Answer 35

Cytokines

Question 36

increase vascular permeability; cause smooth muscle contraction; stimulates mucus secretion; chemoattractants for T cells, eosinophils, mast cells, and basophils.

Answer 36

Arachidonic acid metabolites, lipid mediators (leukotrienes & prostaglandins)