1. DO NOW:  Compare the primary and secondary immune responses, as shown in the graph below.  What is the reason for the differences?

2. B cells

3. B cell activation  B cells can be activated in 2 ways: Contact with antigen Interaction with already activated Helper T cell ○ Cytokine signals  If T H activation, B cell cloning is faster and more plasma cells differentiate

4. B cell activation  APC presents antigen to T H cell: Multiple chemical signals sent back & forth T H cell becomes activated **B cell can be an APC  Activated T H cell releases interleukins which, along with antigen, activates B cell  http://bcs.whfreeman.com/thelifewire/co ntent/chp18/1802004.html http://bcs.whfreeman.com/thelifewire/co ntent/chp18/1802004.html

7. After activation…  Cloning of B cell divides by mitosis  B cells mature into plasma cells Secrete specific antibodies  Plasma cells remain in lymph node but secrete antibodies into lymph/blood

8. Antibody (aka Immunoglobulin) Structure:  Different classes of antibodies

9. How do antibodies work??  Highly specific  Binds to specific part of antigen Epitope  Activates processes that destroy antigen  Labels antigen for destruction, it doesn’t destroy antigen itself

11.  Antigen-antibody complex May inactivate pathogen or toxin ○ Prevent binding to host  Antibodies also trigger complement system Lyse bacteria or microbe

12.  Antigen-antibody complex stimulates phagocytosis

13. http://www.learner.org/channel/courses/biology/archive/ animations/hires/a_hiv1_h.html

14. Memory  Primary immune response 1 st exposure to antigen Antibodies appear in 3-14 days After recognition, antibodies build up for several days then decline  Secondary immune response Circulating memory T & B cells persist Memory cells more sensitive & respond more quickly Booster shots

15. Active vs. Passive Immunity  Active Natural Artificial  Passive Natural Artificial