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Hypersensitivity, Schemes and Mind Maps of Immunology

King Faisal University (KFU)Immunology

– Caused by PMNs and eosinophils during first 2 hours. – Then the mononuclear cells arrive… – All fight any infectious agent injected by the mosquito bite… Type ...

Typology: Schemes and Mind Maps

2021/2022

Uploaded on 09/07/2022

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1
Hypersensitivity
• Chapter 25
• Types of Hypersensitivity
• Immunological mechanisms of Hypersensitivity
• Factors that predispose to Hypersensitivity
• Clinical manifestations of Hypersensitivity
2
Hypersensitivity
3
Cells in Hypersensitivity Reactions
• A - in skin and
mucosal tissues
• B - Granulocytes:
circulate in the blood
and extravasate into
tissues
• C - Mononuclear
cells: monocytes
(macrophage) and
lymphocytes
4
3 Types of Hypersensitivity
pf3
pf4
pf5

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1

Hypersensitivity

  • Chapter 25
  • Types of Hypersensitivity
  • Immunological mechanisms of Hypersensitivity
  • Factors that predispose to Hypersensitivity
  • Clinical manifestations of Hypersensitivity 2

Hypersensitivity

3

Cells in Hypersensitivity Reactions

  • A - in skin and mucosal tissues
  • B - Granulocytes: circulate in the blood and extravasate into tissues
  • C - Mononuclear cells: monocytes (macrophage) and lymphocytes 4

3 Types of Hypersensitivity

5

Type I Immediate

Hypersensitivity

6

Type I Immediate Hypersensitivity

  • Example Mosquito bites: the swelling and redness
  • 1 st bite generates immune response to mosquito salivary protein antigens = - IgE antibodies are produced.
  • IgE abs are immobilized on surface of Mast cells by high affinity IgE FcR
  • 2 nd bite: salivary Ag bind IgE.
    • Signal transduction to Mast cells to release histamine and serotonin into tissues
  • Capillary endothelial cells pull apart and fluids seep into tissues bringing in Complement and cytokines 7

Type I Immediate Hypersensitivity

  • Example Mosquito bites: itching sensation
  • Histamine binds to type c nerve fibers that sense pain and initiate the itching sensation
  • A “wheal”or fluid-filled itchy bump is formed.
  • Further induction of capillary dilation and “flare” reaction develops - increased redness
  • More scratching results in more extensive dilation of capillaries 8

Type I

Immediate

Hypersensitivity

13

  • Origins of

Allergic

Responses

  • Dendritic cells, macrophage, and eosinophils likely bring allergens to the lymph nodes for B cell activation and Switching to IgE 14

Common Allergens

  • Exposure to allergens varies based on season and location 15

IgE FcR

Activation

  • Cross-linking of

IgE FcR results in

signal transduction

and subsequent

mast cell

degranulation

16

Mast Cell Activation and Degranulation

  • Cross linking of IgE FcR

leads to signal transduction

events:

  • cAMP production
  • Activated PKC
  • Elevated intracellular

calcium levels

17

Mast Cell Activation and Degranulation

  • Active PKC

phosphorylates granule

membrane proteins

  • Permeability to water and

calcium changes

  • Granules swell, migrate,

fuse with the membrane

and release their granules

18

Mast Cell Activation and Degranulation

  • Cross linking of IgE

FcR leads to signal

transduction events:

  • Production of

Arachidonic acid

  • Production of PG,

TX, and LT

  • Acute inflammation 19

Asthma

  • Inflammatory disease of the small bronchioles of the lung
  • Lungs of asthmatics have significant inflammation affecting all layers of the bronchiolar tissue
  • Involves multiple cell types
  • Surface is coated with a thicker layer of mucus
  • Underlying tissues are packed with eosinophils and activated lymphocytes
  • Smooth muscle of airways is thickened and hyperreactive
  • Bronchioles contain high densities of mast cells that are armed with allergen specific IgE 20

Asthma Attack

  • Initiation occurs when a sensitized individual is exposed

to the allergen that binds IgE on mast cells

  • Bronchiolar restrictive response begins in minutes
  • Caused by release of histamines from mast cells
    • Smooth muscle response to histamines causes contraction
  • Release of Arachidonic acid and derivatives (PG, LT,

TX) from mast cells triggers second wave of airway

constriction

  • Neutrophils and eosinophils move into airways
  • Severe compromise of oxygen and carbon dioxide exchange

25

Type II

Hypersensitivity

  • Erythroblastosis

fetalis or

  • hemolytic disease of

the newborn

26

ABO Blood Group Antigens

27

  • Autoantibodies

against Type IV

collagen in the

lungs and

kidneys

  • Results in

complement

activation and

neutrophil

influx

  • Tissue damage

Goodpasture Disease