Type IV Hypersensitivity REVISED
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10 Terms
What is type IV hypersensitivity mediated by?
CD4 Th1 cells
Briefly describe the pathogenesis of Type IV
Type IV is mediated by CD4 Th1 cells, leads to secretion of IFN-y which causes macrophage activation (CD8 T cells can sometimes be involved)
What is a clinically relevant example of type IV hypersensitivity?
Tuberculosis (granulomas)
What is the main tool to diagnose tuberculosis?
Tuberculin test
What can lead to a false positive for a tuberculin test?
Other mycobacteria, nocardia
What can lead to a false negative on a tuberculin test?
Late or early stage of infection, decreased immune response (from old age)
What are examples of haptens?
Urushiol, antibiotics, metals, insecticides
What is contact allergy dermatitis mediated by?
Cd4 and CD8 T cells (TH1 response)
What is the one condition that is mediated by CD8 T cells?
Toxic epidermal necrolysis
What is toxic epidermal necrolysis?
TEN is an almost-always drug associated disease where metabolites of the drug attach to keratinocytes. CD8 T cells develop modified antigens that kill the keratinocytes, leading to severe systemic signs and widespread painful skin lesions. This can lead to the epidermis detaching and infection of the skin, leading to sepsis.