University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

241

Pages:

2
Author:

Mariam A. A.

TYPE II HYPERSENSITIVITY ~cytotoxic hypersensitivity~ Antibody-dependent cell-mediated cytotoxicity Failure of control tolerance Self-reactive B & T cells escape B cells activated by antigens Chemotactic factors attract neutrophils Release pro-inflammatory substances Tissue damage 1st cytotoxic mechanism Complement product makes a hole in cell C5b, C6-C9 binding Fluid flows in → cell bursts & cell lysis 2nd cytotoxic mechanism Antibody binds to antigen on host cells Macrophages recognize Fc portion of antibody Phagocytosis 3rd cytotoxic mechanism IgG antibody coats antigen on RBC bound by C3b Complement system activated Opsonization Phagocytosis 4th cytotoxic mechanism Antibody binds to Fc portion of antibody on cell bound to IgG Cell dysfunction Cellular destruction (e.g., Grave's disease) Diagnosis If suspect direct Coombs test Separate RBC from plasma Mix with Coombs reagent (anti-human globulin) If RBC agglutinate (clumps up) Indicates antibodies or complements in serum Indirect Coombs test Check for blood group incompatibility Mix patient serum with lab RBCs with known antigens on their surface Mix with Coombs reagent (anti-human globulin) Check for agglutinates Determines if have antibodies before exposed to antigen E.g., mismatched blood transfusions, 2nd pregnancy with mismatched blood types, RF factor