Tag: Type I Hypersensitivity

Type I Hypersensitivity

Type I Hypersensitivity


Introduction

  • Rapidly developing immunological reaction
  • Occur within minutes
  • Wheal & flare reaction
  • Combination of an antigen with antibody bound to mast cells in individuals previously sensitized to the antigen.
  • Mast cells are the most important cells.
  • Eosinophils are the most important cells in the late phase reaction .
  • Histamine is the most important mediator.
  • IL-4 is essential for turning on IgE secreting B cells.
  • PAF is the most important cytokine in the initiation of late phase reaction.
  • Most potent eosinophilic activating cytokine is IL-5. 

Exposure occurs

  • By inhalation (respiratory route)
  • Ingestion (GIT) of antigen.

Etiology

  • Genetic
  • Pollutants
  • Viral

Body parts generally they include:

  • nose: allergic rhinitis (hay fever)
  • eye: allergic conjunctivitis
  • skin: hives
  • soft tissue: angioedema
  • lungs and airways: asthma
  • generalised in the body: anaphylaxis and death if not treated.

Peak action time

  • 15-30 mins

Two phases :-

Initial response

  • After first antigen exposure, antigen presented to CD-4 helper T cells (TH2 type) by antigen presenting cells.
  • Primed TH2 cells release IL-4 that acts on B-cells to form Ig E specific for that particular antigen.
  • IgE bind to the surface receptors of mast cells and basophils.
  • This act as sensitization (prior sensitization)
  • First exposure is also called priming or sensitizing exposure (dose).
  • Subsequent exposure (shocking dose) to same antigen
  • Result in activation of mast cells and basophils with release of mediator from these cells that leads to:
  • Smooth muscle spasm
  • Increase mucus secretion from the epithelial cells.
  • Vasodilatation
  • Increased vascular permeability
  • Recuritment of inflammatory cells

Late phase response

  • Additional leukocytes are recruited.
  • Cells amplify and sustain the inflammatory response without additional exposure to the triggred antigen.
  • Eosinophils produce major basic protein and eosinophilic cataionic protein that are toxic to epithelial cells.
  • Platelet activating factor (PAF) recruits and activates inflammatory cells 
  • PAF important cytokine in the initatiation of late phase response.

Type I hypersensitivity occurs in two forms

  1. Anaphylaxis      →            Acute, potentially fatal, systemic.
  2. Atopy                 →           Chronic, Nonfatal, Localized.

Examples

  • Urticaria
  • angioedem
  • hay fever
  • some forms of asthma
  • eczema
  • Anaphylactic shock
  • Casoni’s test
  • Theobald Smith phenomenon
  • Schultz Dale phenomenon
  • Prausnitz Kustner (PK) reaction

 Type I hypersensitivity test

  • Injection is given subcutaneously or intradermally (usually in the forearm).
  • The site is examined after 20 minutes.
  • Examples → Casoni’s testsensitivity testing of drug.
Exam Question
 

Introduction

  • Rapidly developing immunological reaction
  • Occur within minutes
  • Wheal & flare reaction
  • Combination of an antigen with antibody bound to mast cells in individuals previously sensitized to the antigen.
  • Mast cells are the most important cells.
  • Eosinophils are the most important cells in the late phase reaction .
  • Histamine is the most important mediator.
  • IL-4 is essential for turning on IgE secreting B cells.
  • PAF is the most important cytokine in the initiation of late phase reaction.
  • Most potent eosinophilic activating cytokine is IL-5.

Examples

  • Urticaria
  • angioedem
  • hay fever
  • some forms of asthma
  • eczema
  • Anaphylactic shock
  • Casoni’s test
  • Theobald Smith phenomenon
  • Schultz Dale phenomenon
  • Prausnitz Kustner (PK) reaction

 Type I hypersensitivity test

  • Injection is given subcutaneously or intradermally (usually in the forearm).
  • The site is examined after 20 minutes.
  • Examples → Casoni’s test, sensitivity testing of drug.
Don’t Forget to Solve all the previous Year Question asked on Type I Hypersensitivity

Type I Hypersensitivity

TYPE I HYPERSENSITIVITY

Q. 1

Which among the following is an example for type I hypersensitivity reaction?

 A

Casoni’s test

 B

Arthus reaction

 C

Graves disease

 D

Pernicious anemia

Q. 1

Which among the following is an example for type I hypersensitivity reaction?

 A

Casoni’s test

 B

Arthus reaction

 C

Graves disease

 D

Pernicious anemia

Ans. A

Explanation:

Type I reactions (ie, immediate hypersensitivity reactions) involve immunoglobulin E (IgE)–mediated release of histamine and other mediators from mast cells and basophils.

Casoni’s test, intradermal injection of hydatid fluid followed by production of wheal-flare reaction denotes hydatid infection. It is an immediate hypersensitivity reaction (Type I).

Arthus reaction is a type of local type III hypersensitivity reaction. Type III hypersensitivity reactions are immune complex-mediated, and involve the deposition of antigen/antibody complexes.

The autoimmune diseases, Myasthenia gravisGraves’ disease and Pernicious anemia are examples of Type II hypersensitivity.


Q. 2

Examples of type 1 hypersensitivity is –

 A

Lepromin test

 B

Tuberculin

 C

Casoni’s test

 D

Arthus reaction

Q. 2

Examples of type 1 hypersensitivity is –

 A

Lepromin test

 B

Tuberculin

 C

Casoni’s test

 D

Arthus reaction

Ans. C

Explanation:

Ans. is ‘c’ i.e., Casoni’s test


Q. 3

Type 1 hypersensitivity includes all of the following except –

 A

Autoimmune hemolytic anemia

 B

Anaphylaxis

 C

Extrinsic asthma

 D

Hay fever

Q. 3

Type 1 hypersensitivity includes all of the following except –

 A

Autoimmune hemolytic anemia

 B

Anaphylaxis

 C

Extrinsic asthma

 D

Hay fever

Ans. A

Explanation:

Ans. is `a’ i.e., Autoimmune hemolytic anemia

Autoimmune hemolytic anemia is type 11 HSN.


Q. 4

Wheal & flare reaction is what type of hypersensitivity reaction?

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Q. 4

Wheal & flare reaction is what type of hypersensitivity reaction?

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Ans. A

Explanation:

Ans. is ‘a’ i.e., Type 1


Q. 5

Spring catarrh is which type of hypersensitivity reaction –

 A

type I

 B

type II

 C

type II & III

 D

All

Q. 5

Spring catarrh is which type of hypersensitivity reaction –

 A

type I

 B

type II

 C

type II & III

 D

All

Ans. A

Explanation:

Ans. is ‘a’ i.e., Type I

. Vernal keratoconjuctivitis is a recurrent, bilateral, external ocular inflammation primarily affecting boys and young adults living in warm, dry climates.

. It is an allergic disorder in which IgE (type I) and cell mediated immune mechanisms (type IV) play an important role.


Q. 6

Examples of type I hypersensitivity is:

 A

Tepromin test

 B

Tuberculin

 C

Casoni’s test

 D

Arthrus reaction

Q. 6

Examples of type I hypersensitivity is:

 A

Tepromin test

 B

Tuberculin

 C

Casoni’s test

 D

Arthrus reaction

Ans. C

Explanation:

Answer is C (Casoni’s test) :

Casoni’s test is an immediate H.S. type skin test (type I) that detects, positive reaction (wheal) in response to intradermal injection of fresh sterile Hydatid fluid


Q. 7

Which of the following is true about anaphylaxis:

September 2007

 A

It is mediated by allergen specific IgE

 B

Type-I hypersensitivity reaction

 C

Cytokines like IL4, IL5 and IL6 along with histamine is released

 D

All of the above

Q. 7

Which of the following is true about anaphylaxis:

September 2007

 A

It is mediated by allergen specific IgE

 B

Type-I hypersensitivity reaction

 C

Cytokines like IL4, IL5 and IL6 along with histamine is released

 D

All of the above

Ans. D

Explanation:

Ans. D: All of the above

Anaphylaxis is an acute multi-system severe type I hypersensitivity reaction.

Based on the pathophysiology, anaphylaxis can be divided into “true anaphylaxis” and “pseudo-anaphylaxis” or “anaphylactoid reaction.”

The symptoms, treatment, and risk of death are the same; however, “true” anaphylaxis is caused by degranulation of mast cells or basophils mediated by immunoglobulin E (IgE), and pseudo-anaphylaxis occurs without IgE mediation


Q. 8

IL-5 is released in which hypersensitivity reaction:

September 2011

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Q. 8

IL-5 is released in which hypersensitivity reaction:

September 2011

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Ans. A

Explanation:

Ans. A: Type I

T-helper2 (Th2) cells release IL4, IL5, GM-CSF and other local factors that lead to an influx of eosinophils and tissue damage in contact dermatitis type of type IV hypersensitivity reaction


Q. 9

Immunoglobulin involved in Type I hypersensitivity reaction:     

March 2013 (b)

 A

IgA

 B

IgM

 C

IgE

 D

IgG

Q. 9

Immunoglobulin involved in Type I hypersensitivity reaction:     

March 2013 (b)

 A

IgA

 B

IgM

 C

IgE

 D

IgG

Ans. C

Explanation:

Ans. C i.e. IgE

Immunoglobulins

  • First antibody to be synthesized after primary immunization: IgM
  • First antibody to be synthesized after exposure to new antigen: IgM
  • First antibody to be synthesized by fetus: IgM
  • Antibody which fixes complement: IgM
  • Only immunoglobulin that crosses placenta: IgG
  • Immunoglobulin found in mucous secretions (saliva, tears, colostrum etc.): IgA/secretory antibody
  • Immunoglobulin elevated in atopic diseases (asthma, hay fever etc.): IgE
  • Immunoglobulin mediating reaginic hypersensitivity: IgE

Q. 10

Allergic BPA which kind of hypersensitivity reaction ‑

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Q. 10

Allergic BPA which kind of hypersensitivity reaction ‑

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Ans. A

Explanation:

Ans. is ‘a’ i.e., Type I


Q. 11

MAST cells play a central role in the development of which type of hypersensitivity reaction?

 A

Immediate

 B

Antibody mediated

 C

Cell mediated

 D

Immune complex mediate

Q. 11

MAST cells play a central role in the development of which type of hypersensitivity reaction?

 A

Immediate

 B

Antibody mediated

 C

Cell mediated

 D

Immune complex mediate

Ans. A

Explanation:

Ans. is ‘a’ i.e., Immediate


Q. 12

Allergic rhinitis is which type of hypersensitivity reaction?

 A

Type -1

 B

Type-2

 C

Type-3

 D

Type-4

Q. 12

Allergic rhinitis is which type of hypersensitivity reaction?

 A

Type -1

 B

Type-2

 C

Type-3

 D

Type-4

Ans. A

Explanation:

 

Pathogenesis of allergic rhinitis

Allergic rhinitis is a type I hypersensitivity. It occurs in two phases:‑

1) Initial response/Acute or early phase

After first antigen exposure, this antigen is presented to CD-4 helper T cells (TH2 type) by antigen presenting cells. These primed TH, cells release IL-4 that acts on B-cells to form Ig E specific for that particular antigen. The antigen specific Ig E antibodies then bind to the surface receptors of mast cells and basophils. The process from first antigen exposure to the coating of mast cells by Ig E acts as sensitization (prior sensitization) and first exposure is also called priming or sensitizing exposure (dose). Subsequent exposure (shocking dose) to same antigen then results in activation of mast cells and basophils with release of inflammatory mediators 

  1. Histamine (most important)
  2. PAF
  3. Heparin
  4. Cytokines (IL-1, 3, 4, 5, 6; INF)
  5. Leukotriens (B4, Ch D4)
  6. Eosinophil chemolactic factor (ECF)
  7. PGD2
  8. Neutrophil chemolactic factor (NCF)
  • The release of these mediators result in : –
  1. Increased vascular permeability and vasodilatation which result in tissue edema – Nasal blockage and sneezing.
  2. Smooth muscle spasm → Bronchoconstriction
  3. Hyperactivity of glands → Rhinorrhea
  4. Recruitment of inflammatory cells.

2) Late phase response

  • Recruited inflammatory cells of initial phase amplify and sustain the inflammatory response without additional exposure to the triggered antigen. PAF is the most important mediator in initiation of late phase response. Eosinophils are particularly important cells among the recruited cells which also include neutrophils, basophils, monocytes and T-cells. It causes symptoms like nasal congestion and post nasal drip.



Q. 13

Atopy in hypersensitivity is ‑

 A

Systemic type I hypersensitivity

 B

Local type I hypersensitivity

 C

Systemic type II hypersensitivity

 D

Local type II hypersensitivity

Q. 13

Atopy in hypersensitivity is ‑

 A

Systemic type I hypersensitivity

 B

Local type I hypersensitivity

 C

Systemic type II hypersensitivity

 D

Local type II hypersensitivity

Ans. B

Explanation:

Ans. is `b’ i.e., Local type I hypersensitivity


Q. 14

In this image this arrow represent which type of hypersensitivity reaction?

 A

Type -1

 B

Type-2

 C

Type-3

 D

Type-4

Q. 14

In this image this arrow represent which type of hypersensitivity reaction?

 A

Type -1

 B

Type-2

 C

Type-3

 D

Type-4

Ans. A

Explanation:

This arrow represent Allergic rhinitis

Pathogenesis of allergic rhinitis

Allergic rhinitis is a type I hypersensitivity. It occurs in two phases:‑

1) Initial response/Acute or early phase

After first antigen exposure, this antigen is presented to CD-4 helper T cells (TH2 type) by antigen presenting cells. These primed TH, cells release IL-4 that acts on B-cells to form Ig E specific for that particular antigen


Q. 15

This condition as shown in image is an example of which type of hypersensitivity reaction

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Q. 15

This condition as shown in image is an example of which type of hypersensitivity reaction

 A

Type I

 B

Type II

 C

Type III

 D

Type IV

Ans. B

Explanation:

Erythroblastosis fetalis

Ans. is ‘b’ i.e., Type II

  • Erythroblastosis fetalis and blood transfusion reactions are type II hypersensitivity reactions.

Q. 16

The reaction (Arrows) shown in Photograph is a which type of hypersensitivity reaction? 

 A

Type 1.

 B

Type 2.

 C

Type 3.

 D

Type 4.

Q. 16

The reaction (Arrows) shown in Photograph is a which type of hypersensitivity reaction? 

 A

Type 1.

 B

Type 2.

 C

Type 3.

 D

Type 4.

Ans. A

Explanation:

Ans:A.)Type 1.

The reaction shown in the picture above represents wheal-and-flare reaction ,which is a type1 reaction.

Wheal and Flare reaction

  • If the antigen is injected beneath the skin—for example, by the sting of an insect or in the course of some medical procedure—the local reaction may be extensive. Called a wheal-and-flare reaction, it includes swelling, produced by the release of serum into the tissues (wheal), and redness of the skin, resulting from the dilation of blood vessels (flare).

Hypersensitivity reaction

  • Hypersensitivity is a set of undesirable reactions produced by the normal immune system, including allergies and autoimmunity. 
Type Alternative names Often mentioned disorders Mediators
I Allergy (immediate)
  • Atopy
  • Anaphylaxis
  • Asthma
  • Hives
  • Allergic Rhinitis
  • Wheal and Flare reaction
  • IgE
II Cytotoxic, antibody-dependent
  • Autoimmune hemolytic anemia
  • Rheumatic heart disease
  • Thrombocytopenia
  • Erythroblastosis fetalis
  • Goodpasture’s syndrome
  • Graves’ disease
  • Myasthenia gravis 
  • IgM or IgG
  • (Complement)
  • MAC
III Immune complex disease
  • Serum sickness
  • Arthus reaction
  • Rheumatoid arthritis
  • Post streptococcal glomerulonephritis
  • Membranous nephropathy
  • Lupus nephritis
  • Systemic lupus erythematosus
  • Extrinsic allergic alveolitis (hypersensitivity pneumonitis)
  • IgG
  • (Complement)
  • Neutrophils
IV Delayed-type hypersensitivity, cell-mediated immune memory response, antibody-independent
  • Contact dermatitis.
  • Mantoux test
  • Chronic transplant rejection
  • Multiple sclerosis
  • Celiac Disease
  • Hashimoto’s thyroiditis – Some type 2. Mostly type 4.
  • T-cells
V Autoimmune disease, receptor mediated 
  • Graves’ disease
  • Myasthenia gravis
  • IgM or IgG
  • (Complement)



Q. 17

A hypersensitivity reaction is shown in the image.From the following options,which option is an example of this type of reaction?

 A

Autoimmune Hemolytic Anemia

 B

Drug induced Vasculitis

 C

Anaphylaxis

 D

Tuberculin reaction

Q. 17

A hypersensitivity reaction is shown in the image.From the following options,which option is an example of this type of reaction?

 A

Autoimmune Hemolytic Anemia

 B

Drug induced Vasculitis

 C

Anaphylaxis

 D

Tuberculin reaction

Ans. C

Explanation:

Ans:C.)Anaphylaxis.

Type I hypersensitivtiy reaction is shown in the image.


Q. 18

Allergic hypersensitivity is mediated by ‑

 A

IgM

 B

IgG

 C

IgD

 D

IgE

Q. 18

Allergic hypersensitivity is mediated by ‑

 A

IgM

 B

IgG

 C

IgD

 D

IgE

Ans. D

Explanation:

Ans. is ‘d’ i.e., IgE



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