7. definition(type 4 hypersensitivity)
Type 4 hypersensitivity is often called delayed type hypersensitivity as the
reaction takes two to three days to develop.
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. CD4+ T cells secrete IL-2 and interferon gamma, further inducing
the release of other Th1 cytokines, thus mediating the immune response.
Activated CD8+ T cells destroy target cells on contact, whereas activated
macrophages produce hydrolytic enzymes and, on presentation with certain
intracellular pathogens, transform into multinucleated giant cells
8. Hero's of type 4 hypersensitivity
TDTH cells/TC/Th1
Cytokines:IL-2,MIF,TNF,interferon.
Macrophages ,lytic enz.
9. Type 4 hypersensitivity
Contact hypersensitivity
Small
molecules
complex with
skin proteins
Complex
internalized by
APC
Response 48-72 hrs
12. Figure 44–4 • Type IV hypersensitivity. Type IV
responses are mediated by T cells through three
different pathways. In the first, type 1 helper T
(TH1) cells recognize soluble antigens and release
interferon-γ (IFN-γ) to activate effector cells, in
this case macrophages (Mø), and cause tissue
injury. In TH2-mediated responses, eosinophil's
predominate. TH2 cells produce cytokines to
recruit and activate eosinophil, leading to their
degranulation and tissue injury lymphocytes
(CTLs). In the third pathway, damage is caused
directly by cytolytic T. IL, interleukin."
13. Example of type 4 hypersensitivity
Contact dermatitis (poison ivy rash, for example)
Temporal arteritis
Symptoms of leprosy
Symptoms of tuberculosis
Transplant rejection
Coeliac disease
