hypersensitivities/ infections “the immune system gone bad”
Post on 22-Dec-2015
226 views
TRANSCRIPT
![Page 1: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/1.jpg)
Hypersensitivities/ Infections
“The Immune System Gone Bad”
![Page 2: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/2.jpg)
Hypersensitivities
1. Allergies – Exaggerated immune response against environmental antigens
2. Autoimmunity – immune response against host’s own cells
3. Alloimmunity – immune response against beneficial foreign tissues, such as transfusions or transplants
![Page 3: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/3.jpg)
These immune processes initiate inflammation and destroy healthy tissue. Four types:
Type I – IgE-mediated allergic reactions
Type II – tissue-specific reactions
Type III – immune-complex-mediated reactions
Type IV - cell-mediated reactions
![Page 4: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/4.jpg)
Type I - IgE-mediated allergic reactions or immediate hypersensitivity
Characterized by production of IgE
Most common allergic reactions
Most Type I reactions are against environmental antigens - allergens
![Page 5: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/5.jpg)
Sometimes beneficial to host – IgE-mediated destruction of parasites
![Page 6: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/6.jpg)
Selected B cells produce IgE
Need repeated exposure to large quantities of allergen to become sensitized
IgE binds by Fc end to mast cells after first exposure
![Page 7: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/7.jpg)
Second exposure (and subsequent exposures) – antigen binds with Fab portion of antibody on mast cells, and cross-links adjacent antibodies, causing mast cell to release granules.
Response is immediate ( 5- 30 minutes)
![Page 8: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/8.jpg)
![Page 9: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/9.jpg)
Histamine release:• Increases vascular permeability, causing
edema
• Causes vasodilation
• Constricts bronchial smooth muscle
• Stimulates secretion from nasal, bronchial and gastric glands
• Also hives (skin), conjunctivitis (eyes) and rhinitis (mucous membranes of nose).
![Page 10: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/10.jpg)
Late phase reaction• 2 – 8 hours; lasts for 2 - 3 days
• Other mediators that take longer to be released or act:– Chemotactic factors for eosinophils and
neutrophils– Leukotrienes– Prostaglandins– Protein-digesting enzymes
![Page 11: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/11.jpg)
![Page 12: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/12.jpg)
Treatment• First wave – antihistamines or epinephrine
(blocks mast cell degranulation)
• Second wave – corticosteroids and nonsteroidal anti-inflammatory agents that block synthesis of leukotrienes and prostaglandins
• Desensitization by repeated injections of allergen – formation of IgG
![Page 13: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/13.jpg)
Anaphylaxis – Type I allergic reaction
may be localized or general
immediate – within a few minutes of exposure
Systemic anaphylaxis:pruritus(intense itching)urticaria (hives)Wheezing; dyspnea; swelling of the larynx
Give epinephrine
![Page 14: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/14.jpg)
Anaphylactic shock
• Hypotension, edema (esp. of larynx), rash, tacycardia, pale cool skin, convulsions and cyanosis
• Treatment:– Maintain airway– Epinephrine, antihistamines, corticosteroids– Fluids– Oxygen
![Page 15: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/15.jpg)
Can be life threatening, so individuals should be aware
• Skin tests – injection – see wheal and flare
• Lab tests for circulating IgE
![Page 16: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/16.jpg)
Type II – Tissue specific reactions(antibody-dependent cytotoxicity)
• Most tissues have specific antigens in their membranes expressed only by that tissue
• Antibodies bind to cells or surface of a solid tissue (glomerular basement membrane)
![Page 17: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/17.jpg)
Destruction of tissue occurs:– Destruction by Tc Cells which are not
antigen specific
– Complement-mediated lysis
– Phagocytosis by macrophages(“frustrated phagocytosis”)
– Binding of antibody causes cell to malfunction
![Page 18: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/18.jpg)
![Page 19: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/19.jpg)
Type III – Immune-complex-mediated reactions
• Caused by antigen-antibody complexes formed in circulation and deposited in vessel walls or other tissues
• Not organ specific
• Effects caused by activation of complement – chemotaxis of neutrophils
• Neutrophils release lysosomal enzymes into tissues (“frustrated phagocytosis”)
![Page 20: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/20.jpg)
![Page 21: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/21.jpg)
Type IV- Cell- mediated reactions• Sensitized T lymphocytes – either Tc Cells
or lymphokine producing Td cells• Takes 24 – 72 hours to develop• Damage by Tc Cell or inflammatory
response by Td Cells (lymphokines)• Graft rejection, tumor rejection, TB reaction,
poison ivy and metal reactions• Immune diseases• Tissue rejection
![Page 22: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/22.jpg)
![Page 23: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/23.jpg)
![Page 24: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/24.jpg)
Systemic lupus erythematosus SLE
Autoanitbodies against nucleic acids and other self components
![Page 25: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/25.jpg)
Infection - viral
• Viruses extremely small – can infect bacteria
• Usually just composed of DNA (or RNA) + protein “coat” or capsid
• Can’t reproduce on their own – need to use a host cell
![Page 26: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/26.jpg)
Infection
• Adsorbed to host cell receptor
• Penetration
• Coat removal
• Uses host enzymes to replicate nucleic acid and proteins
• New viruses are assembled
• Virus is released– Lytic cycle
![Page 27: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/27.jpg)
![Page 28: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/28.jpg)
![Page 29: Hypersensitivities/ Infections “The Immune System Gone Bad”](https://reader036.vdocuments.site/reader036/viewer/2022062421/56649d7a5503460f94a5e92e/html5/thumbnails/29.jpg)
Cellular effects
• Decreased synthesis of host proteins
• Disruption of lysosomal membranes
• Changes in host cell membrane proteins
• Transform into cancer cell
• Tissue damage may promote bacterial infection