1. Infectious Diseases Unit 5 Lesson 4 plan

2. Can someone please explain : – Each B and T cell receptor is unique because it was made randomly. – So, if only one B cell has a receptor that recognizes H1N1, how could this lone cell control the infection? Do Now

3. 1. B cells with antigen receptors 2. Bind to a specific antigen 3. Then begin to replicate – clonal expansion increases the pool of B cells available. Remember, only the antigen specific cells respond. This creates a pool of adaptive recognition specialists! Clonal expansion As soon as B and T cells bind antigen they begin to replicate – this is called clonal expansion!

4. Clonal expansion takes place in the lymph nodes

5. The clone (group) of B cells. two target the pathogen in two ways 6. They are called effector cells. 4. The clone can release the receptor from the cell surface as antibodies 1. A B cell with a specific receptor 2. Binds to its specific antigen 3. Then replicates – clonal expansion 5. Or it can stay on the cell surface to remember the antigen for the next time. 7. They are called memory cells.

6. B cell antibodies: 1.Clump the pathogens and neutralize them. 2.Increase phagocytosis of the pathogens. 3.Increase the functions of complement. T cells: 1.Killer T cells kill infected host cells 2.Helper T cells help innate cells, B cells and other T cells to function. How do B and T cells work?

7. So there is cross talk between the innate immune system and the adaptive immune system Antibodies work in three ways:

8. Killer T cells kill infected host cells 1. The T cell’s specific receptor recognizes the foreign antigen on the cell surface Killer T cell Infected cell 2. Killer T cells release Enzymes that enter the infected host cell 3. The enzymes encourage the infected cell to commit suicide Cell suicide is called apoptosis – it is an active process whereas death is passive. enzymes

9. Helper T cells activate effector B cells and T killer cells with cytokines

10. Activity Combine everything you now know about the immune response to assign the sequence of events as the body responds to a pathogen.

11. Putting it all together – Fill in how it works

12. Putting it all together –

13. Adaptive responses do the rest Innate responses clear 99% of infections And they don’t forget.. The bottom line…

14. Homework Review your notes on immune barriers and the innate and adaptive immune responses. Make sure you understand them!