This document discusses T cell-mediated hypersensitivity reactions, which are caused by inflammation from cytokines produced by CD4+ T cells and cell killing by CD8+ T cells. CD4+ T cell-mediated hypersensitivity plays a major role in autoimmunity, while CD8+ T cell-mediated hypersensitivity acts against viral infections, tumors, and graft rejection. The inflammatory reactions stimulated by CD4+ T cells can be divided into the activation of CD4+ T cells by antigen presenting cells, and the responses of differentiated effector T cells.

2.  Caused by inflammation resulting from cytokines produced by
CD4+ T cells and cell killing by CD8+ T cells.
 Also known as T cell mediated hypersensitivity.
 CD4+T cell mediated hypersensitivity:
Major role in autoimmunity.
 CD8+T cell mediated hypersensitivity:
Predominantly acts against viral infection, tumor cells and
graft rejection.

3. In CD4+ T cell-mediated hypersensitivity reactions, cytokines
produced by the T cells induce inflammation that may be
chronic and destructive.
The prototype of T cell-mediated inflammation is delayed-type
hypersensitivity(DTH).
Both Th1 and Th17 are involved in immune mediated
destruction.

4. The inflammatory reactions stimulated by CD4+ T cells can
be divided into two stages:
Activation of CD4+T cells.
Responses of differentiated effector T cells.

5. Activation of CD4+T cells:
CD4+ T cells recognize peptides
. In displayed by APC
IL-2 secreted by CD4+ T cells
Proliferation of CD4+ T cells and activation of
APC(macrophages & dendritic cells)