A state of incr. or excessive response to the presence of an antigen (foregin protein or allergen) to which the client has been previously exposed
Discuss Type 1: Immediate hypersensitivity
-most common allergic rxn
-occurs w/in minutes of exposure to antigen
-reaction of IgE antibody on mast cells w/ antigen which results in release of meiators, esp. histamine
-e.g.: asthma, anaphylaxis
Discuss Type 2: Cytotoxic or antibody-mediated hypersensitivity.
-characterized by antibody formation against an antigen
-e.g. autoimmune hemolytic anemia and Goodpasture's disease
Discuss Type 3: Immune complex-mediated hypersensitivity
-characterized by antibody-antigen complexes that cause vessel or tissue injury
-e.g. RA, autoimmune diseases, SLE, vasculitis
Discuss Type 4: cell-mediated hypersenstivity
-characterized by sensitized T-lymphocytes releasing cytokines that cause cytotoxicity or delayed-typer hypersensitivity
-e.g.: PPD, transplant rejection, Graves
Describe the patho of Type 1 hypersenstivity
1)pt. exposed to allergen
2)person makes antigen-specific IgE which binde to basophils and mast cell. Once antigen-specifif IgE is formed pt. is sensitized
3)pt. has 2nd exposure to allergen
4) Primary phase: antigen binds to 2 IgE molecules on surgace of basophil or mast cell, distorting cell membrane. Histamine is released causing nasal congestion, prutitis, erythema, incr. cap. permeablilty...
Secondary phase: other vasoactive amines draw WBC to the area and stimulate more inflammatory rxn thru biochemicals leukotriene and prostaglandins
What is anaphylaxis?
-an extreme Type 1 hypersensitivity rxn, a uncommon but life-threatening emergency!
-affects multiple organs w/in seconds of exposure to allergen