The difference between active and passive immunity is the fact that active immunity is immunity developed by an individual's cells in response to an infection or upon contact with foreign antigens, and passive immunity is immunity developed when ready-made antibodies are inoculated into the body. Passive immunity is short lived but active immunity is long lasting.
In humoral immunity:
1. B cells, which have antibodies attached to their surface, will bind to an antigen floating around in the blood.
2. Once this occurs, the antigen will be endocytosed and subsequently presented on the surface of the B cell in a MHC class 2 receptor
3. A T-Helper 2 cell containing the same antibody will bind to the MHC class 2 receptor on the B-cell
4. This will cause the B-cell to differentiate into plasma cells and memory B-cells
5. Plasma cells generate free floating antibodies, memory B-cells stay around in case of later infection
In the Cell-Mediated response:
1. A macrophage eats a pathogen/antigen
2. The antigen is presented on the surface of the macrophage in a MHC class 2 receptor
3. A T-helper 1 cell with the corresponding antibody on its surface binds to the MHC class 2 receptor containing the antigen
4. The T-helper 1 cell then activates cytotoxic T cells
5. Cytotoxic T cells then patrol your body looking for other infected cells. Infected cells will have the antigen presented on the surface of the cell in a MHC class 1 receptor.
6. When the cytotoxic T cell finds an infected cell, it will bind to the MHC class 1 receptor containing the antigen
7. The cytotoxic T cell will then release Interferon and Tumor Necrosis Factor. The former slows down the infected cell's reproduction, while the latter causes the cell to undergo apoptosis.
Thus, the Humoral system takes down pathogens floating in the blood, while the Cell-Mediated response kills cells that have become infected with the pathogen