Cell Mediated Immunity response-T cells

-T-cells are formed in bone marrow and mature in thymus gland by forming specific type of T cell receptor (TCR) on outer surface of plasma membrane.

-3 types of T cell with specific type are produced from thymus gland:
.T helper cell (Th)
.T cytotoxic cell (Tc)
.T suppressor cell (Ts)
-Macrophage that is involved in 2nd line of body defense mechanism does phagocytosis of pathogen.
-The pathogen are destroyed in cell through action of hydrolytic enzyme released by lysosome.
-Smaller pieces of pathogen known as antigen is bind to Major Histo-Compatibility Complex(MHC) to form antigen-MHC complex.
-The antigen-MHC complex is attached to outer surface of plasma membrane to enable the macrophage to function as antigen presenting cell (APC)
-When APC encounter Th cell that has complementary TCR to its antigen-MHC complex, the APC binds to the Th cell.

-Then, the APC secretes Interleukin 1 (IL1)
-IL1 stimulates Th cells to secrete Interleukin 2 (IL2)
-Secretion of IL2 stimulates the Th cell to divide through mitosis to form memory cells and large number of effector Th cells.
-Effector Th cell secretes more IL2.
-Increase in IL2 concentration stimulates mitosis cell division of Tc cell that have the same type of TCR with the Th cell.
-Tc cell divide to form memory cells and large number of effector Tc Cells.
-Effector Tc cells scouts for cells that are infected with the same type of pathogen.
-Cells that are infected are recognized by identification of antigen-MHC complex on plasma membrane of infected cells.

-The effector Tc cells binds complementarilary to the complex on plasma membrane of effector cell, it then secretes perforin.
-Perforin arranges on plasma membrane of infected cells, peforation of plasma membrane of infected cell occurs, lysis of the infected cells occurs.
-The effector Tc cells then scouts for other infected cells that have same type if antigen-MHC complex.

-Once immunity is achinved, Ts cell suppress action of Tc and Th cells.
-The binding occurs between MHC complex on APC with TCR on Th cell.