Biology__Topic 6__T6L7 Flashcards
What are lymphocytes?
white blood cells that help to defend the body against specific diseases. They circulate in the blood and lymph
What are lymph nodes?
Filter interstitial fluid. Swollen glands mean you are fighting an infection. They contain lymphocyte reserves
What are the different types of lymphocyte?
B cells and T cells
What do lymphocytes respond to?
Antigens (proteins and other chemicals that are ‘foreign’) not normally found in the body.
What is the response by lymphocytes called?
specific immune response
Where are B lymphocytes produced?
bone marrow
When are B lymphocyte cells activated?
(Each B cell has one specific type of antigen receptor on its surface.) When its receptor binds to an antigen with the complementary shape.
How do B lymphocytes behave when activated?
Secrete antibodies Which bind to antigens on the microbe cell surface membrane. Which act as labels, allowing phagocytes to recognise and destroy the cell
What are antibodies?
Special protein molecules called immunoglobulins
Why are B cells special
Each B cell binds to only one specific antigen
Where are T lymphocytes produced?
bone marrow
Where do T lymphocytes mature?
thymus gland
Describe T cells
T cells have one specific type of antigen receptor on their surface. This only binds to an antigen with the complementary shape.
What are the two types of T cells?
T helper cells and T killer cells
What are T helper cells?
When activated, they release cytokines, stimulating the B cells to divide and become cells capable of producing antibodies. They also enhance the activity of phagocytes.
What are T killer cells?
Destroy any cells with antigens on their surface membrane that are recognised as foreign or ‘non-self
This includes tissues received as a transplant from another person, and cells infected with pathogens.
How are T-helper cells activated?
Macrophage engulfs bacterium with antigens on surface
Macrophage become Antigen Presenting Cell (APC)
APC bind to T cells that have complementary CD4 receptors on their surface
T helper cell divides to produce a clone of active T helper cells and T memory cells.
What do antigens on the surface of an APC act as?
Signal to immune system that foreign antigens are present
Describe the cloning of B cells
Receptors on B cells bind to complementary foreign antigens and become APCs.
Antigen presenting B cells bind to active cloned T helper cells presenting the same antigen.
T helper cells then release cytokines, stimulating division and differentiation of B cells
How do B cells react to cytokines?
Cytokines stimulate the division and differentiation of B cells.
B cells divide to produce two clones of cells: B effector cells and B memory cells
(B effector cells differentiate to produce plasma cells which release antibodies to blood and lymph)
(B memory cells remain in blood for months or years, enabling secondary immune response)
What is the process of B cell division called?
clonal selection
What do B cells divide to produce under the influence of cytokines?
B effector cells - differentiate to produce plasma cells which release antibodies into blood and lymph. Only live a few days
B memory cells - like T memory cells but longer lived - stay in blood for months/years.
What’s the process of B cell division called? Explain a bit
Clonal selection
The first time a B cell comes across a non self antigen complementary to its cell surface receptors, the primary immune response occurs: where “antibody-producing cell” cell production takes 10-17 days.
During this time, the person is most likely to suffer the symptoms of the infection.
What’s the role of the T killer cells
(How do they destroy cells)
When host cell is infected with bacterium, it may present the antigen on its surface and become an APC.
T killer cell with complementary receptor binds to APC
T killer cells are stimulated by cytokines (from T helper cells) and divide, forming an active clone
T killer cells release enzymes which create pores in membranes of the infected cells.
Water flows into infected cell, which undergoes lysis
What’s the secondary immune response?
If infected by same bacterium/virus, the immune system responds faster
B memory cells produced in primary response immediately differentiate into plasma cells and release antibodies.
Antibody production is greater and response lasts longer
Person often has no symptoms
This person is immune
How do cells in the body know that each other aren’t invading pathogens?
There are specific membrane proteins on cell surface
There are hundreds of alleles for these proteins
So the combination of proteins on the cell surface is unique to an individual.
How come B and T cells never have antigen receptors that are complementary to body cell surface membrane proteins?
They are destroyed by apoptosis (programmed cell death)
What are some examples of the body attacking itself? (AUTOIMMUNE DISEASES)
insulin dependant diabetes
Rheumatoid arthritis
Multiple sclerosis
Diagram for antibody
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