Type IV Hypersensitivity Flashcards
Why is this hypersensitivity considered delayed?
Due to the time needed for T cell proliferation, which mediate this reaction (12hrs - inflammation, 24 - 72 hrs - maximum intensity)
How do T cells mediate this hypersensitivity reaction?
Through cytokines IFN gamma and IL-17, which are associated with Neutrophil and Macrophage recruitment
Describe the general process of Type IV Hypersensitivity reactions.
Antigens are recognized by Langerhans cells, which travel to lymph nodes for presentation to T cells.
Effector T cells travel to the site of infection, where a small portion become Lymphoactin (become specific for that antigen).
Effector T cells secrete cytokines that recruit/ activate Neutrophils and Macrophages, which secrete products that lead to inflammation.
Explain how Granuloma and tubercle formation occurs.
Bacterium consumed, and while very slowly removed, necrode tissue, and surrounding layers of phagocytic cells and APC’s fail to eliminate.
Bacterium can escape and enter lymphatics and neighboring tissues, exploiting macrophage tissue repair processes.
Allergic contact dermatitis is associated with Type IV Hypersensitivity, because -?
Highly reactive allergens combine with skin proteins, acting as haptens. When Effector T cells arrive they attack the epithelial cells creating many vesicles in the process.
