The Hypersensitivity reaction and their types

1. HYPERSENSITIVITY
By HARSHAL S BEHADE
Msc R.G.B.C RTMNU
(Jr and Sr. college teacher)

2. Introduction
 “An exaggerated or undesirable response/reactions by the immune
system to a drug or other substances”

3. Types:-
 There are four types
 Hypersensitivity type 1 immediate type
 Type 2 antibody mediated
 Type 3 immune complex mediated
 Type 4 delayed type

4. Hypersensitivity 1 immediate type
 When allergen are entered into the body, our immune responses or immune
system’s are activates and on working immediately.
 It occurs in two phases:-
a) Sensitisation phase
b) Effector phase

5. Sensitisation phase
 Alergens enter into the body.
 So we have two types of antigen
presenting cells
 1. Dendritic cells
 2. Macrophages
 They breaks allergen into antigen
peptides.
And they show that antigen peptide
To T-cell with the help of MHC-II molicule

6.  Then TH cells detects these antigen
peptide with the help of CD4 receptors.
 Once it detects then TH cells
differentiate into TH2 cells.
 These TH2 cells releases Interlukins
molicules as IL-4, IL-5,IL-13.
 This IL-5 molicules develop & activates
Eosinophils.

7.  Remaining Interlukins 4 & 13 are differentiate
B cells into IgE secreating Plasma cells and Memory cells.
 These plasma & memory cells secreates IgE antibody.
 Some receptors are present in circulating Mast cells FCeRI
(high affinity FC receptors)
So these IgE antibody binds that receptors.

8. 2nd :- Effector phase
 In this phase that allergen enters into the body again or second time (or
introduced again ).
 This is known as shocking dose.
 Allergen directly encounters the F(ab) region of IgE molecule present on Mast
cell.
 & binds with that Fab region
 Then cross linking occurs in IgE molecule & the mast cell initiates into
degranulation.

9. Three changes occurred in mast cell:-
 1. It releases granules contained Histamine and Proteases.
 2. Membrane phospholipase A2 activates by this activity,
 Then they are converted into Arachidonic acid.
 This arachidonic acid makes Prostglandins (D2) by Cox pathway,
 And Leukotriens (B4,C4,O4) by Lox pathway.
 3. also one signal going to Nucleus & then Cytokines gene activates.
 Then this cytokines & chemokines are released.
 So these histamine, protease, prostaglandins, leukotriens, cytokines,
chemokines are our Modulators.

10. Modulators
 These produces our immune response immediately and this occurs within a
minute after repeat exposure.
 These responses are in the form of
 1. Vasodilation
 2. Increases vascular permeability
 3. and smooth muscles contraction
 These immediate responses occurred by granular prostaglandins and
leukotriens.

11. Next is a late phase reaction
(Inflamation)
 After repeate exposure to allergen the inflammation occures in 2-24 hrs,
 by cytokines and chemokines.
1. Leukocytes infiltration
2. Epithilial damages
3. Bronchospasm, occures

12. Menifestations:-
 Systemic anaphylaxis (allergy on full body)
 Localized anaphylaxis
 Systemic:-
 Within minutes after exposure itching(red ness), hives, vomiting, abdominal cramps, diarrhea &
larrhengial abstraction follows and the patient may go into shock & even die within hour’s.
 Allergens : 1. venom ( bee, ants etc)
 2. Drugs ( penicillin, Insuline etc)
 3. Antitoxins
 4. See foods
 5. Nuts
 Drug of choice:- Adrenaline = 0.5ml

13. Localised anaphylaxis:- (atopy)
 A. Allergic Rhinitis (Hey fever)
 Most common atopic disorder.( it affects 10% populations)
 Ex. Symptoms :- high secretion of Cunjuctiva, nasal mucosa, upper respiratory
tract infections, sneezing, coughing.
 B. Asthama:-
 Second most common atopic disorder
 Lower respiratory tract infection involved
 Symptoms:- Bronchospasm, Breathlessness.
 Asthama if allergic then caused by pollen dust fumes, insect products, viral
antigens.
 If it is Intrinsic then coused by excessive exercise, temperature change.

14. c.Food allergy
 Someone are allergic by food like nuts, eggs, seafoods.
 Symptoms: - food poisoning l;ike , vomiting, diarrhea, Atopic urticaria.
 D. Atopic dermatitis
 Erruption on skin filled by pus
 Symptoms:- Erythromatus skin, (eruption which are filled with pus)
 E. Drug allergy:- 1.penicillin, 2. Sulphonamide


15. Treatments
 Avoid contact with known allergens (pollen etc.)
 Hyposensitisation:-
 It was known about the allergy & if we take regular doses intradermaly introduce
in the skin or body then the effect may less then IgG antibody secreats apart from
IgE.
 Monoclonal Anti Ig-E
 Drugs:- 1. Antihistamine
2. Adrenaline
3. Cortisone
4. Theophyline
5. Cromolyn solution.

16. Thank you