Infectious Diseases • Unit 5 Lesson 4 plan
Do Now • 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?
Clonal expansion As soon as B and T cells bind antigen they beginto replicate – this is called clonal expansion! 2. Bind to a specific antigen 1. B cells with antigen receptors 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!
Clonalexpansion takes place in the lymph nodes
The clone (group) of B cells. target the pathogen in two ways 2. Binds to its specific antigen 1. A B cell with a specific receptor 3. Then replicates – clonal expansion 5. Or it can stay on the cell surface to remember the antigen for the next time. 4. The clone can release the receptor from the cell surface as antibodies 6. They are called effector cells. 7. They are called memory cells.
How do B and T cells work? • B cell antibodies: • Clump the pathogens and neutralize them. • Increase phagocytosis of the pathogens. • Increase the functions of complement. • T cells: • Killer T cells kill infected host cells • Helper T cells helpinnate cells, B cells and other T cells to function.
Antibodies work in three ways: So there is cross talk between the innate immune system and the adaptive immune system
Killer T cells kill infected host cells 3. The enzymes encourage the infected cell to commit suicide 1. The T cell’s specific receptor recognizes the foreign antigen on the cell surface 2. Killer T cells release Enzymes that enter the infected host cell Infected cell enzymes Killer T cell Cell suicide is called apoptosis – it is an active process whereas death is passive.
Helper T cells activate effector B cells and T killer cells with cytokines
Activity • Combine everything you now know about the immune response to assign the sequence of events as the body responds to a pathogen.
Putting it all together – Fill in how it works
The bottom line… Innate responses clear 99% of infections Adaptive responses do the rest And they don’t forget..
Homework • Review your notes on immune barriers and the innate and adaptive immune responses. • Make sure you understand them!