Hypersensitivity type 1 reaction with classification .pptx

This ppt is for Hypersensitivity type 1 reaction and will give you a well knowledge and based on Essentials of medical microbiology by Dr. APURBA SHASTRI

1. BY-NITIN YADAV MODERATOR=DR. SR SWARNA MAM

2. LEARNING OBJECTIVES Introduction and Classification Types of Hypersensitivity Reactions Type 1 Hypersensitivity Reaction (a).Overview (b).Experiments to Demonstrate Type 1 Reaction (c).Mechanism of Type 1 Reaction (d). Manifestions (e).Factors Influencing (f).Detection of Type 1 reaction (g).Treatment

3. Introduction Purpose of Immune System=Eliminate foreign antigen In most of times= Lead to localised inflammatory response - to eliminate foreign antigen without any damage But some times= Response become abnormal -Lead to exaggerated inflammatory response -causes Extensive tissue damage

4. ➤ Hypersensitivity :-it is a condition in which an exaggerated or augmented immune response after contact of the antigen that is harmful to the host. ➤ Allergy :- it is refers to all immune process harmful to the host, such as hypersensitivity and autoimmunity.Its some time called atopy. ➤ Sensitizing dose :- the initial contact which is sensitizes the immune system, leading to priming of appropriate B or T lymphocyte. ➤ Shocking dose :- subsequent contact with the allergen causes manifestation of hypersensitivity

5. Gell and Coombs Classification On the basis of time occurrence and Immune response-4 types 1.Immediate type- Type1, Type2, Type3 2.Delayed type – Type 4

6. Hallmark= Production of IgE by sensitized B cells following a contact with an allergen Induce mast cell degranulation Active mediators released from these granules cause- (a).Vasodilation (b).Vascular and smooth muscle contraction (c).Increased vascular permeability Lead to localised (atopy) and systemic response(anaphylaxis)

7. Allergens Foreign substance that induce allergy

8. Experiments to demonstrate Type 1 Rxn . P.K.Reaction By K Prausnitz and H Kustner (1921) -Named P-K antibody or reaginic antibody -Later known as IgE (1960) ➤ Serum, suspected to contain IgE antibody, is drown from allergic patients. ➤ This serum injected intradermally into a non allergic person. ➤ After 24-48 hrs. suspected antigen injected at the same site. Then wheal and flare reaction are developed at the site. This is the 1st to demonstrate that antibodies in the serum are responsible for the allergy and it is transferable from one person to other.

9. Mechanism of Type 1 Hypersensitivity Occurs through two phases- the sensitization and effector phase =both occurring with the interval of 2-3 weeks 1.Sensitization Phase-When exposed to sensitizing or priming dose of an allergen. -Most affective when allergen introduced perenterally -Production of antigen specific IgE 2.Effector Phase- When the same allergen is introduced again -Degranulation and pharmacological actions of chemical mediators

10. 1.Sensitization Phase Type 1 Hypersensitivity step 1: Activation of TH2 Cell and B cell Type 1 Hypersensitivity step 2: Mast cell sensitization

11. 2.Effector phase Type 1 Hypersensitivity step 3: Mast cell reexposer to antigen and degranulation

12. Phase of Degranulation 2 Phases . Primary mediators : The preformed chemical mediators which are already synthesized by mast cells, are immediately released, e.g. histamine and serotonin . Secondary mediators : The mast cells synthesize them following stimulation by allergen and release, e.g. prostaglandins and leukotrienes

13. Manifestation of Type 1 Reaction Grouped into Immediate and late Immediate manifestation=(a).Systemic anaphylaxis (b).Localized anaphylaxis-Allergic rhinitis - Asthma,Food allergy,Atopic dermatitis Late manifestation

14. 1.Immediate Manifestation Systemic Anaphylaxis =Acute medical conition ,which need treatment as early as possible orelse can become fatal -with character like Severe dyspnea,Hypotension and vascular collapse -Occurs within minute of exposure to allergen -Treatment=DOC-Epinephrine(adrenalin)

15. Localised Anaphylaxis(Atopy) - - reaction is limited to a specific target tissue or organ - mostly the epithelial surfaces at the entry sites of allergen - allergies afflict more than 20% of people. -They almost always run in families (i.e. inherited) and are collectively called atopy.

16. 2. Late Manifestations The immediate phase of type 1 reaction is followed, 4–6 hours later, by an inflammatory response. This phase lasts for 1–2 days and leads to tissue damage. Mediators= Released in acute phase along with cytokines(IL-3,IL-4,IL-8) ,ECF and NCF. - Induce recruitment of various inflammatory cells. Eosinophil influx= by ECF,IL-5 and GM-CSF Neutrophil infiltration= induced by NCF and IL-8

17. Detections of Type 1 Hypersensitivity Skin Prick Test Total Serum IgE Antibody Allergen-specific IgE =Various test formats are available like Multiplex immunoblot assay,FEIA,RAST,Automated immunoassay system etc.

18. TREATMENT Avoidance of contact with known allergens: The first and foremost step is identification and avoidance of contact with known allergens such as dusts, house pets, allergic food, etc. Hyposensitization : Repeated exposure to increased subcutaneous doses of allergens can reduce or eliminate the allergic response to the same allergen. ¾ This occurs probably due to either (1) a shift of IgE response towards IgG or (2) a shift of TH2 response towards TH1 response, which secrete IFN -y that in turn can suppress the IgE response ¾ Here, the IgG acts as blocking antibody because it competes with IgE for binding to the allergen. The IgG-allergen immunocomplex can be removed later by phagocytosis.

19. Monoclonal anti- IgE : Humanized monoclonal anti- IgE can bind and block the IgE ; but useful only if the IgE is not already bound to high affinity Fc receptors Drugs: Several drugs are useful in suppressing type 1 response through various mechanisms .

20. Refrences Essential of Medical Microbiology,Third Edition,by Dr. Apurba S Sastry MD (JIPMER) DNB MNAMS PDCR; JAYPEE BROTHERS Medical Publishers Revised reprint 2022

21. THANK YOU