Tags: Disease.
Type 4 hypersensitivity is often called delayed type hypersensitivity as the reaction takes two to three days to develop. Unlike the other types it is not antibody mediated but rather is a type of cell-mediated response.CD4+ helper T cells recognize antigen in a complex with Class 2 major histocompatibility complex. The antigen-presenting cells in this case are macrophages that secrete IL-12 which stimulates the proliferation of further CD4+ Th1 cells.