Type 4 Hypersensitivity Made Easy

Type IV Hypersensitivity

FLASHCARDS and other COOL STUFF :   / medsimplfied  

CHECK OUT OR TSHIRTS : bit.ly/2KaICaE

Type 1 Reaction :    • Hypersensitivity Type 1 Reactions Mad...  

Complement System :    • Complement System Made Easy- Immunolo...  
Type IV hypersensitivity is also called delayed-type hypersensitivity (DTH) because the tissue reaction usually occurs 24 to 48 hours after exposure to antigen. Type IV hypersensitivity is a cell-mediated immunoreaction that is dependent on the presence of a significant number of primed, antigen-specific T cells. This type of reaction is typified by the response to poison ivy, which typically reaches its peak 24 to 48 hours after exposure to antigen.

Plant antigens (haptens) react with and modify cellular proteins that are then targeted by the sensitized T cells. Interaction of CD8+ T cells with antigen presented in the context of class I MHC results in the activation of these T cells and induces them to kill target cells displaying these antigens. APCs also display antigen in the context of class II MHC to activate CD4+ T cells to secrete cytokines, including IL-2, which result in the proliferation of CD8+ T cells. The result of these interactions is the amplification of antigen-specific T cells that initiate the hypersensitivity reaction over the course of a few days.