Antigen presentation and initiation of an adaptive immune response

Step 1

Pathogen is engulfed into a phagosome which fuses with a lysosome

Step 2

pathogen is digested by enzymes in the lysome

Step 3

some of the digested antigen are released by exocytosis

step 4

some of the digested antigen are displayed on the MCH-II receptors on the surface of the macrophage or dendritic cell

step 5 antigen presentation

these cells move to the lymph node and pressent them to naive helper T cells that carry specific receptors for that antigen

step 6

these helper t cells undergo expansion and clones are produced

step 7

helper T cells assist other immune cells by releasing specific cytokines, can initiate either the humoral adaptive immune system or the cell-mediated immune system

Helper T cells

Class of T cells that bind to antigen-MCH-II complexes on antigen-presenting ells and activate B cells and cytotoxic T cells