Infectious DiseasesUnit 5 Lesson 4 plan

• 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

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 expansionAs soon as B and T cells bind antigen they begin to replicate – this is called clonal expansion!

Clonal expansion takes place in the

lymph nodes

The clone (group) of B cells. 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.

• 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 cells2. Helper T cells help innate cells, B cells and

other T cells to function.

How do B and T cells work?

So there is cross talk between the innate immune system and the adaptive immune system

Antibodies work in three ways:

Killer T cells kill infected host cells

1. The T cell’s specific receptor recognizes the foreign antigenon the cell surface

Killer T cell

Infected cell

2. Killer T cells releaseEnzymes that enterthe 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

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

Putting it all together –

Adaptive responsesdo the rest

Innate responsesclear 99% of infections

And they don’t forget..

The bottom line…

Homework

• Review your notes on immune barriers and the innate and adaptive immune responses.

• Make sure you understand them!