Infectious Diseases Unit 5 Lesson 3 plan
Jan 12, 2016
Infectious DiseasesUnit 5 Lesson 3 plan
Do now
• Why might the innate response be unable to control an infection?
• What happens then?
Do now
• Why might the innate response be unable to control an infection?
• What happens then?
• What is ADAPTIVE IMMUNITY?
Do now• What is adaptive immunity?• What happens when innate responses don’t
control the infection?
B lymphocytes are made in the blood– Secrete antibodies
T lymphocytes are made in the thymus– Some help activate immune system responses.– Others attack and kill cells infected with
bacteria or viruses.
Adaptive immune cells are called
Lymphocytes.
• Antigens are:– Not usually found in the host – they are specific to the
pathogen.– They are recognized by a specific receptors on B and T
cells.
The T cell receptor binds antigen that is presented by an innate cell
Adaptive cells ‘see’ Antigens
The B cell receptor can be attached to the cell surface …
….or released from the cell surface as an antibody.
Small group brainstorming:
• At your table, take 10 minutes to complete the worksheet.
Each B and T cell responds to only one antigen
– There are millions of kinds of B cells and T cells
– Each randomly makes one antigen receptor.– They wait in the lymphatic system.– If they ‘see’ their antigen they will respond.
Only the B cells that ‘see’ their antigen respond!
Antigen
How do B cells recognize ‘their’ antigen?
• B cells bind to extracellular antigen.• They cannot ‘see’ an antigen that is inside cells!
• T cells only bind to antigen when it is presented to them by an antigen presenting host cell
• T cells can ‘see’ both extracellular and intracellular antigens!
Extracellular antigen (bacterial infection)
How do T cells recognize ‘their’ antigen?
• T cells only bind to antigen when it is presented to them by an antigen presenting host cell
• T cells can ‘see’ both extracellular and intracellular antigens!
Intracellular antigen (viral infection!)
How do T cells recognize ‘their’ antigen?
How do B and T cells respond?
At your table, discuss the following question:
– 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?
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!
As soon as B and T cells bind an antigen they begin to replicate – this is called clonal expansion!
Clonal expansion
Homework
• Write one paragraph that summarizes the main points of today’s lesson.