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Hypersensitivity Reactions type IV

Hypersensitivity Reactions type IV. PhD. student kefah F.Hasson 2014. Characteristics Interaction of primed T cells and associated antigen Involve reactions by T memory cells. Reactions are delayed by one or more days (delayed type hypersensitivity -DTH) .

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Hypersensitivity Reactions type IV

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  1. Hypersensitivity Reactions type IV PhD. student kefahF.Hasson 2014

  2. Characteristics • Interaction of primed T cells and associated antigen • Involve reactions by T memory cells. • Reactions are delayedby one or more days (delayed type hypersensitivity -DTH) . • Infiltration of Mononuclear Cells ( Inflammatory response).

  3. Delayed is relative because DTH response arise 24-72 hours after exposure rather than within minutes. • Delay is due to migration of macrophages and T cells to site of foreign antigens. • Reactions are frequently displayed on the skin: itching, reddness, swelling, pain

  4. Mechanism of type IV hypersensitivity • Inflammation and tissue injury mediated • by CD4+Th1. • Immune injury mainly caused by infiltration of mononuclear cells and lymphocytes , release cytokines . • 2) Cytotoxicityof CD8+CTL

  5. BACTERIA M.tuberculosis Brucella abortus Listeria monocytogen • Virus Measles Herpes simplex • Fungus Histoplasma Candida • protozoa Leishmania • Others Ivy poison Hairs dye Metals poison Nickel salts INTRACELLULAR PATHOGENS INDUCE DELAYED TYPE

  6. Effector phase

  7. Diseases of Type IV (Cell-Mediated) : • Infectious delayed type hypersensitivity like : OT( Old Tuberculin ) test. • 2) Contact dermatitis :like water blister . • 3) Acute rejection of allogenic • transplantation .

  8. Allergic Contact Dermatitis Response to Poison Ivy

  9. Granuloma Formation from DTH Mediated by Chronic Inflammation

  10. THANK YOU

  11. Four types of Hypersensitivity Reactions Type II Type I Ag Target cell Y Y Y Y IgG IgE Target cell Fc receptor Fc recep- tor Killer cell Y Mast cells Ab Histamine Complement Type III Type IV Ag Ag Y Complement Y Th Th cell Endothelial cells Ab Macrophage Y Y Cytokines Neutrophils Activated Macrophage

  12. Topic for exam • The Gall & Coombs classification of hypersensivity reactions . • Type I ,II ,III ,IV hypersensivity reactions mechanism & example . • Immunological basis of the HDN caused by Rh incompatibility . • Mention the common diseases of each types of hypersensivity reactions.

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