hypersensitivity types of hypersensitivity.pptx

Hypersensitivity types cell mediated hypersensitivity and antibody mediated

1. Hypersensitivity reactions are harmful antigen-specific immune response,occur when an individual who has been primed by an innocuous antigen subsequently encounters the same antigen,produce tissue injury and dysfunction. It is defined as a state of exaggerated immune response to an antigen. TYPES OF HYPERSENSITIVITY REACTION- Type 1 or Immediate Type 2 or antibody mediated Type 3 or Immune complex mediated Type 4 or Delayed type HYPERSENSITIVITY REACTIONS

2. TYPE 1 HYPERSENSITIVITY REACTION: It occur in a previously sensitized individual It is triggered by binding of an antigen to IgE antibody on the surface of mast cells Mast cells activate and release inflammatory mediators SEQUENCE OF EVENTS- Allergen is inhaled/eaten/injected Allergen stimulates T H 2 production T H 2 cell secretes cytokines: IL-4 stimulates B cells to make IgE IL-5 recruits eosinophils IL-13 stimulates mucous secretion

3. Mast cell binds IgE Allergen bridges IgE on mast cell Mast cell degranulates

4. Reminder: Where do inflammatory mediators come from? Complement proteins Coagulation factors Factors XII, XI, X, etc.

5. Local reactions skin: itching, hives GI: diarrhea lung: bronchoconstriction Anaphylaxis itching, hives, erythema constriction of bronchioles, wheezing laryngeal edema, hoarseness vomiting, cramps, diarrhea laryngeal obstruction shock DEATH

6. TYPE 2 HYPERSENSITIVITY “Antibody-mediated” hypersensitivity Antibodies bind to antigens on cell surface Macrophages eat up cells, complement gets activated, inflammation comes in SEQUENCE OF EVENTS Antibody binds to cell surface antigen one of the following mechanism takes place- A)opsonization and phagocytosis

7. B) Inflammation and complement breakdown products C)antibody mediated cellular dysfunction

8. Opsonization and phagocytosis

9. Cellular dysfunction Graves disease Myasthenia gravis

10. Inflammation

11. Type II Hypersensitivity Disease Antigen Symptoms Autoimmune hemolytic anemia RBC antigens, drugs Hemolysis Pemphigus vulgaris Proteins between epithelial cells Bullae Goodpasture syndrome Proteins in glomeruli and alveoli Nephritis, lung hemorrhage Myasthenia gravis Acetylcholine receptor Muscle weakness Graves disease TSH receptor Hyperthyroidism

12. TYPE 3 HYPERSENSITIVITY “Immune complex-mediated” hypersensitivity Antibodies bind to antigens, forming complexes Complexes circulate, get stuck in vessels, stimulate inflammation Leads to inflammationand tissue injury

13. Type III Hypersensitivity Disease Antigen Symptoms Systemic lupus erythematosus Nuclear antigens Nephritis, skin lesions, arthritis… Post-streptococcal glomerulonephritis Streptococcal antigen Nephritis Polyarteritis nodosa Hepatitis B antigen Systemic vasculitis Serum sickness Foreign proteins Arthritis, vasculitis, nephritis Arthus reaction Foreign proteins Cutaneous vasculitis

14. Type III Hypersensitivity Systemic immune complex disease complexes formed in circulation deposited in several organs example: serum sickness Local immune complex disease complexes formed at site of antigen injection precipitated at injection site example: Arthus reaction Two kinds of type III hypersensitivity reactions

15. Type IV Hypersensitivity T CELLS “T-cell-mediated” hypersensitivity Also known as delayed type of hypersensitivity Activated T cells do one of two things: release cytokines that activate macrophages, or kill cells directly This process is normally useful against intracellular organisms (viruses, fungi, parasites) Leads to inflammation, cell destruction, granuloma formation

16. Type IV Hypersensitivity Delayed-type hypersensitivity CD4+ T cells secrete cytokines macrophages come and kill cells Direct cell cytotoxicity CD8+ T cells kill targeted cells Two kinds of type IV hypersensitivity

17. Delayed-Type Hypersensitivity (DTH)

18. Prolonged DTH can lead to granulomatous inflammation Perivascular CD4+ T cells replaced by macrophages Macrophages are activated, look “epithelioid” Macrophages sometimes fuse into “giant cells” Granuloma = collection of epithelioid macrophages Prolonged DTH can lead to granulomatous inflammation Perivascular CD4+ T cells replaced by macrophages Macrophages are activated, look “epithelioid” Macrophages sometimes fuse into “giant cells” Granuloma = collection of epithelioid macrophage

19. Type IV Hypersensitivity CD8+ T cell recognize antigens on the surface of cells T cells differentiate into cytotoxic T lymphocytes (CTLs) which kill antigen-bearing cells CTLs normally kill viruses and tumor cells In T-cell mediated cytotoxicity, CTLs kill other things: Transplanted organ cells Pancreatic islet cells (Type I diabetes) T-cell-mediated cytotoxicity

20. T-Cell-Mediated Cytotoxicity