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Delayed type hypersensitivity, Type IV
T cell mediated hypersensitivity reaction occuring more then 24 hrs after contact with the antigen
Delayed type hypersensitivity characeristics
an influx of nonspecific inflammatory cells, mostly macrophages into tissues. Lacks antibody involvement
not always detrimental - but can cause extensive tissue damage and plays an important role in host defense against intracellular pahtogens and contact antigens
causative agents of type IV hypersensitivity rxn
bacteria, fungi, protozoa, noninfectious agents (chemicals)
peptide epitopes and MHC class II proteins, CD4+ T cells associate to result in
a ell mediated response and the generation of memory Tdth cells
purified protein derivative, results in activation nof memory Th1 cells by APC and intiation of DTH
activated Tdth cells
secrete cytokines that result in vasodilation, increased vascular permeability, and recruitment/activation of macrophages
tissue damage in DTH
results from release of hydrolytic enzymes and reactive oxygen intermediates from macrophages
granulomas formation due to
1. persistance of particles in macrophage, 2. persistant immune complexes, 3. chronic irritants
ACD characterized by
48-72 hr delayed eczematous response to the epicutaneous application of the antigen
epidermal langerhans cells
modified self proteins in ACD internalized by these cell and then migrate as veiled cell to regional lymph nodes
poison ivy lesion origin
lysis of altered epidermal cells by CD8+ T cells and lytic enzymes released from activated macrophages
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