UNIT 3 - KA6
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What are the two types of lymphocytes
There are two types of lymphocyte, B lymphocyte and T lymphocyte
What are lymphocytes
Lymphocytes are white blood cells involved in the body’s specific immune response
What do lymphocytes respond to
Lymphocytes respond to specific antigens on the pathogens surface.
Explain the term specific in relation to immunity
Acts on a particular pathogen only
What is an antigen
Antigens are molecules often proteins located on the surface of cells that trigger a specific immune response
Which type of receptors do each lymphocyte have
Lymphocytes have a single type of membrane receptor which is specific for one antigen
What does antigen binding lead to
Antigen binding leads to repeated lymphocyte division resulting in the formation of a clonal population of identical lymphocytes
What do B lymphocytes produce against antigens
B lymphocytes produce antibodies against antigens this leads to the destruction of the pathogen
What are antibodies
Antibodies are Y shaped proteins that have receptor binding sites specific to a particular antigen on a pathogen
Explain how antibodies prevent the pathogen causing further infection
Antibodies become bound to antigens, inactivating the pathogen. The resulting antigen-antibody complex can then be destroyed by phagocytosis
Which substances can B lymphocytes respond to
B lymphocytes can respond to antigens on substances that are harmless to the body e.g pollen
What is the hypersensitive response in which b lymphocytes can respond to antigens on substances that are harmless to the body
This hypersensitive response is called an allergic reaction
How do T lymphocytes destroy infected body cells
T lymphocytes destroy infected body cells by recognising antigens of the pathogen on the infected cells membrane and inducing apoptosis.
What is apoptosis
Apoptosis is programmed cell death
Describe the main events in apoptosis of an infected cell
T lymphocytes attach onto infected cells and release proteins. These proteins diffuse into the infected cells causing production of self destructive enzymes which cause cell death.
How are the remains of dead cells removed from the tissue
• virus particles are broken down along with cell components and are not released into the body so cannot cause further infection. They are removed by phagocytosis
What can T lymphocytes normally distinguish
T lymphocytes can normally distinguish between self antigens on the body’s own cells and non self antigens on the infected cells
What happens as a result of failure of regulation of the immune system
Failure of the regulation of the immune system leads to T lymphocytes responding to self-antigens.
What is a self antigen
A self antigen is on a persons own body cells so that the immune system does not launch an attack
What causes auto immune disease
Failure of the regulation of the immune system leads to T lymphocytes responding to self antigens. This causes autoimmune diseases
What happens in autoimmunity
In autoimmunity, the T lymphocytes attack the bodys own cells
What autoimmune diseases are a result of T lymphocytes attacking the body’s own cells
This causes autoimmune disease such as type 1 diabetes and rheumatoid arthritis
What happens to some of the cloned B and T lymphocytes
Some of the cloned B and T lymphocytes survive long term as memory cells
Describe how memory cells rescind to a secondary exposure to the same antigen
When a secondary exposure to the same antigen occurs, these memory cells rapidly give rise to a new clone of specific lymphocytes these destroy the invading pathogens before the individual shows symptoms