1. Foreign substance recognition inside the cell.
   1. A virus has invaded the body through a break in the skin, and has made its way inside a cell. Take us through the pathophysiology that will take place.
2. Virus inserted into host cell - produces viral proteins from taking over the cells machinery (thus antigens)
   1. Takes place in: Spleen, lymph nodes, adenoids, tonsils, Peyer's Patches (intestines), and the appendix
      1. APC function - Antigen presentation molecule
         1. IL-1
         2. Th - Helper T cell - formed in Thymus
            1. IL-2 (self stimulating)
            2. Th - FUNCTIONAL
            3. Th1 cell
            4. Immunocompetent T cell
            5. Plasma Cells
            6. TCR - T cell receptor
            7. Cytokine from IL-2 from the Th1 completes activation
            8. Effector T cells
            9. Tc - Cytotoxic T cell
            10. Time to kill!
            11. Memory Cell
            12. Topic
            13. Expresses CD8
            14. Th2 cell
            15. MHC II - major histocompatibility complex
            16. Immunocompetent B Cell - Th2 reads antigen on B
            17. Plasma Cells
            18. Memory Cell
            19. Topic
            20. CD4 protein = Cellular
3. Virus inserted into host cell - produces viral proteins from taking over the cells machinery (thus antigens)
4. MHC Class 1
5. CD8
6. IL-12 effects Th and becomes Th1
7. IL-4 effects Th and becomes Th2
8. Some of the antigen-specific T and B cells that are activated to rid the body of infectious organisms become long-lived "memory" cells. Memory cells have the capacity to act quickly when confronted with the same infectious organism at later times. It is the memory cells that cause us to become "immune" from later reinfections with the same organism.