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  • 1. Microbiology Hypersensitivity and Allergy Presenter: Jaycris C. Agnes 3SED-SC
  • 2. Hypersensitivity and Allergy Hypersensitivity-An exaggerated immune response that may cause damage to the host. The trigger is often an innocuous antigen Allergy-A hypersensitive response to an environmental antigen. Often presents as “hay fever”, asthma, dermatitis or anaphylaxis.
  • 3. Four types of Hypersensitivity Immediate-Type Hypersensitivity: Type I (Anaphylactic/ Allergic Reactions)  IgE-mediated  e.g.most common allergies Type II (Cytotoxic Reactions)  IgG-mediated  e.g.ABO transfusion reaction
  • 4. Four types of Hypersensitivity  Type III (Immune Complex Reactions)  Immune-complex mediated  e.g.serum sickness Delayed-Type Hypersensitivity:  Type IV (Cell Mediated Reaction)  T cell-mediated; delayed type  e.g.tuberculin reaction
  • 5. Type I Hypersensitivity  Allergens  Proteins  Examples: drugs, foods, house dust, insect venom, latex, mold spores, & pollens.  Atopy-Predisposition to type I hypersensitivity (atopic people)  Higher levels of circulating IgE  Greater numbers of eosinophils
  • 6. Type I Hypersensitivity  Factors in the Development of Type I Hypersensitivity:  Nature of Antigen  Route of entry  Amount of antigen  Ability to produce IgE antibodies  Frequency of exposure  Length of exposure time
  • 7. Table 1. Pharmacologic Mediators of Immediate Hypersensitivity  MEDIATOR Preformed mediators in granules histamine bronchoconstriction, mucus secretion, vasodilatation, vascular permeability tryptase proteolysis kininogenase kinins and vasodilatation, vascular permeability, edema ECF-A (tetrapeptides) attract eosinophil and neutrophils
  • 8. Newly formed mediators leukotriene B4 basophil attractant leukotriene C4, D4 same as histamine but 1000x more potent prostagland ins D2 edema and pain PAF platelet aggregation and heparin release: microthrombi
  • 9. Type I Hypersensitivity  Localized Anaphylaxis  Allergic reaction takes place in specific part of the body.  Systemic Anaphylaxis  Allergic Reaction takes place in different parts of the body.
  • 10. Type I Hypersensitivity
  • 11. Type I Hypersensitivity  Clinical manifestations  Allergic rhinitis  Asthma  Food allergies  Systemic anaphylaxis
  • 12. Type II Hypersensitivity  Cell associated antigens  Transfusion reactions  Hemagglutinins  Complement mediated  Clinical symptoms include fever, chills, nausea
  • 13. Type II Hypersensitivity  A typical Type Hypersensitivity reaction might follow these sequence: 1. A particular drug binds to the surface of the cell. 2. Anti-drug antibodies then bind to the drug. 3. This initiates complement activation on the cell surface. 4. The complement cascade leads to the lysis of the cell.
  • 14. Type II Hypersensitivity  Erythroblastosis fetalis  Rh+ fetus born to Rh- mother  First pregnancy sensitizes  Subsequent pregnancies result in anti Rh Ab  Mild to severe anemia in fetus  Rhogam
  • 15. Type II Hypersensitivity  Drug induced hemolytic anemia  Some antibiotics can be antigenic  Bind nonspecifically to RBC surface proteins  Ab fixes C and lyses RBCs
  • 16. Type III Hypersensitivity  Immune complexes consist of antigen and antibodies bound together.  Diseases involved are Systemic Lupus Erythematosus and rheumatoid arthritis.
  • 17. Type IV Hypersensitivity  T cell mediated  T helper 1 cells  Effector response is through macrophages not T cytotoxic cells  Cytokine mediated  IL3 Hematopoiesis  Interferon, TNF, IL 1 Extravasation  MCAF Attracts macrophages  MIF Retains macrophages
  • 18.    Delayed hypersensitivity reactions Type Reaction time Clinical appearance Histology Antigen and site contact 48-72 hr eczema lymphocytes, followed by macrophages; edema of epidermis epidermal ( organic chemicals, poison ivy, heavy metals, etc.) tuberculin 48-72 hr local induration lymphocytes, monocytes, macrophages intradermal (tuberculin, lepromin,etc.) granuloma 21-28 days hardening macrophages, epitheloid and giant cells, fibrosis persistent antigen or foreign body presence (tuberculosis, leprosy, etc.)
  • 19. Type IV Hypersensitivity Positive Result for TB skin test 1. Within 2-3 hours after injection of the PPD (Purified Protein Derivative), there is an influx of polymorphonuclear cells into the site. 2. This is followed by an influx of lymphocytes and macrophages while PMN’s dispersed.
  • 20. Type IV Hypersensitivity 3. Within 12-18 hours, the area become red (erythematous) and swollen (edematous). 4. The erythema (redness) and edema (swell) reach maximum intensity bet. 24-48 hours. 5. With time, as the swelling and redness disappear, the lymphocytes and macrophages disperse.
  • 21. Five possibilities why TB skin test may be positive:  A person has tuberculosis.  A person has tuberculosis in the past.  A person has been infected by M. tuberculosis, but the organism has been killed by that person’s host defence mechanism.  A person harvors live M. tuberculosis but does not have TB.  A person had received BCG (Bacille de Calmette et Guérin) vaccine.
  • 22. Table 5  -  Comparison of Different Types of hypersensitivity Characteristics type-I (anaphylactic) type-II (cytotoxic) type-III (immune complex) type-IV (delayed type) antibody IgE IgG, IgM IgG, IgM None antigen exogenous cell surface soluble tissues & organs response time 15-30 minutes minutes-hours 3-8 hours 48-72 hours appearance weal & flare lysis and necrosis erythema and edema, necrosis erythema and induration histology basophils and eosinophil antibody and complement complement and neutrophils monocytes and lymphocytes transferred with antibody antibody antibody T-cells examples allergic asthma, hay fever erythroblastosis fetalis, Goodpasture's nephritis SLE, farmer's lung disease tuberculin test, poison ivy, granuloma
  • 23. Autoimmune Diseases  Autoimmune Diseases result when a person’s immune system can no longer recognizes certain body tissues as “self” and attempt to destroy those tissues.
  • 24. Immunosuppression  Acquired Immunodeficiency maybe caused by drugs, irradiation, or certain infectious diseases.  Inherited Immunodeficiency diseases are inherited immune diseases.
  • 25. H.I.V.
  • 26. WHAT IS HIV??  “Human Immunodeficiency Virus”  A unique type of virus (a retrovirus)  Invades the helper T cells (CD4 cells) in the body of the host (defense mechanism of a person)  Threatening a global epidemic.  Preventable, managable but not curable.
  • 27. OTHER NAMES FOR HIV  Former names of the virus include:  Human T cell lymphotrophic virus (HTLV- III)  Lymphadenopathy associated virus (LAV)  AIDS associated retrovirus (ARV)
  • 28. WHAT IS AIDS ???  “Acquired Immunodeficiency Syndrome”  HIV is the virus that causes AIDS  Disease limits the body’s ability to fight infection due to markedly reduced helper T cells.  Patients have a very weak immune system (defense mechanism)  Patients predisposed to multiple opportunistic infections leading to death.
  • 29. AIDS (definition)  Opportunistic infections and malignancies that rarely occur in the absence of severe immunodeficiency (eg, Pneumocystis pneumonia, central nervous system lymphoma).  Persons with positive HIV serology who have ever had a CD4 lymphocyte count below 200 cells/mcL or a CD4 lymphocyte percentage below 14% are considered to have AIDS.
  • 30. Modes of HIV/AIDS Transmission
  • 31. Through Bodily Fluids  Blood products  Semen  Vaginal fluids
  • 32. IntraVenous Drug Abuse  Sharing Needles  Without sterilization Increases the chances of contracting HIV  Unsterilized blades
  • 33. Through Sex  Unprotected Intercourse  Oral  Anal
  • 34. Mother-to-Baby  Before Birth  During Birth
  • 35. NATURAL COURSE OF HIV/AIDS
  • 36. Stage 1 - Primary  Short, flu-like illness - occurs one to six weeks after infection  Mild symptoms  Infected person can infect other people
  • 37. Stage 2 - Asymptomatic  Lasts for an average of ten years  This stage is free from symptoms  There may be swollen glands  The level of HIV in the blood drops to low levels  HIV antibodies are detectable in the blood
  • 38. Stage 3 - Symptomatic  The immune system deteriorates  Opportunistic infections and cancers start to appear.
  • 39. Stage 4 - HIV  AIDS  The immune system weakens too much as CD4 cells decrease in number.
  • 40. Opportunistic Infections associated with AIDS CD4<500  Bacterial infections  Tuberculosis (TB)  Herpes Simplex  Herpes Zoster  Vaginal candidiasis  Hairy leukoplakia  Kaposi’s sarcoma
  • 41. Opportunistic Infections associated with AIDS CD4<200  Pneumocystic carinii  Toxoplasmosis  Cryptococcosis  Coccidiodomycosis  Cryptosporiosis  Non hodgkin’s lymphoma
  • 42. CD4 <50  Disseminated mycobacterium avium complex (MAC) infection  Histoplasmosis  CMV retinitis  CNS lymphoma  Progressive multifocal leukoencephalopathy  HIV dementia Opportunistic Infections associated with AIDS