Ch21 Cell-mediated defense: CD4 Activation & co-stimulation

Step 6 co-stimulation

In order to fully activate the T h Cell, co-stimulation must occur in which a protein on the APC is recognized by a protein on the T h Cell (double hand shake)

Step5

The APC then wanders around looking for a CD4 cell to present the foreign antigen. (Might find it in the bld or lymph node most likely since lymphocytes will live in a lymph node) Once the APC finds the Helper T Cell, the T cell receptor (idle) then binds to the antigen. Tight bind - forgeign antigen

step4

The ClassII MHC with the exogenous atigen is then loaded & displayed on the APC's surface

Step 2

The class II MHC with the invariant chain is then packaged into a vesicle

Step 1 CD4 activation & co-stimulation

The rough endoplasmic reticulumin in the APC synthesizes a Class II MHC protein which is then loaded with an invariant chain.

Step 3

The vesicle containing the Class II MHC loaded with the invariant chain that combines with a phagolysosone containing bacteria fragments.the invariant chain is then remived fromthe Class II MHC & replaced with a bacterial fragment or other wise known as an exogenous antigen. Exo=outside