HYPERSENSITIVITY

HYPERSENSITIVITY

type 1
1. immediate @ anaphylactic
2. localized & systemic
3. allergy
4. 2 part mechanisms
  1. sensitization upon initial exposure
  2. degranulation of sensitized cells
    1. reexposures -> allergen bind to allergen-specific -> cross linkage -> sensitized cell activation -> synthesis of newly formed mediators
      1. may lead to ANAPHYLAXIS REACTION ( shock )
type 2
1. cytotoxic h/s
2. IgM / IgG react with antigens on cell/tissue
3. 3 syndromes
  1. blood transfusion reaction
    1. blood A, B, AB, O
    2. differ on surface antigen of RBC
    3. ntigen bind to transfused RBC -> complement pathway -> lysis of blood cells
  2. haemolysis diseases
    1. due to rhesus antigen of RBC
    2. Rh(+)- with rh antigen
    3. Rh(-) - no rh antigen
    4. Rhogam - anti-Rh serum
  3. Drug-induced hypersensitivity
    1. drugs -> complex formed -> foreign to host -> antibodies produced -> complenet lysis or phagocytosis
    2. destruction of platelets - inhibit ability clotting blood correctly
type 3
1. immune complex h/s
  1. complex escape phagocytosis and complement -> circulate -> trap in organ, joint and tissue -> trigger mast cells to degranulate -> damage the site
2. 1. localized immune complex disease
3. 2. systematic immune complex disease
type 4
1. cell mediated type h/s
2. DTH responses -> Th1 secrete cytokinesis -> recruited cells secrete lytic enzymes -> damage to tissue
3. occured in response to small chemical encountered with skin
contact hypersensitivity
1. too small to stimulate immune response in free form
2. CH response : similar to DTH
Autoimmune Disease
1. immune response againts one or more self antigen
2. Classifications
  1. 1. Organ specific AD
  2. 2. Non-organ specific AD
3. it happens by :
  1. 1. complement-mediated lysis
  2. 2. Opsonisation
  3. 3. Inhibition of receptor function
  4. 4. Stimulation of receptors
  5. 5. Blockage of biological function
  6. 6. Deposition of immune complexes
4. Causes of AD
  1. 1. Genetic
  2. 2. Environmental
    1. a) infectious agent
    2. b) drugs
    3. c) toxins & pollutants
  3. 3. Loss of immunotolerance
    1. caused by :
      1. a) production of high-affinity autoantibody
      2. b) Generation of autoreactive T cells
      3. c) Autoantibodies produced by autoreactive B cells in absence of T cells

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	Created by Atika Subari over 8 years ago