Neurobiology and Immunology: Specific Cellular Defences Against Pathogens
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What are lymphocytes?
White blood cells that are involved in the specific immune response
What do lymphocytes do?
Respond to specific antigens on invading pathogens
What are antigens?
Antigens are molecules, often proteins, located on the surface of cells that trigger a specific immune response
Lymphocytes have a single type of membrane receptor which is specific for one antigen. What does antigen binding lead to?
Repeated lymphocyte division, resulting in the formation of a clonal population of identical lymphocytes
What are the two types of lymphocyte?
B lymphocytes and T lymphocytes
What do B lymphocytes do?
Produce antibodies against antigens leading to the destruction of the pathogen
What are antibodies?
Y-shaped proteins that have receptor binding sites which are specific to a particular antigen on a pathogen
What do antibodies do?
Become bound to antigens, inactivating the pathogen
What happens to the resulting antigen - antibody complex?
It can be destroyed by phagocytosis
What can B lymphocytes do?
Respond to antigens on substances that are harmless to the body, such as pollen. This hypersensitive response is called an allergic reaction
What do T lymphocytes do?
Destroy infected body cells recognising antigens of the pathogen on the cell and inducing apoptosis
What is apoptosis?
Programmed cell death
T lymphocytes attach to infected cells and release what?
Proteins
What happens to the proteins released?
They diffuse into the infected cells, bringing about the production of self-destructive enzymes which cause cell death. The remains of the cell are then removed by phagocytosis
What happens to the remains of the cell?
Removed by phagocytosis
What can T lymphocytes normally do?
Distinguish between self antigens on the body’s own cells and non-self antigens on infected cells
Failure of the regulation of the immune system leads to what?
T lymphocytes respond to self antigens. This causes autoimmune diseases
What happens in autoimmunity?
The T lymphocytes attack the body’s own cells
What does autoimmunity cause?
Autoimmune diseases such as Type 1 Diabetes and Rheumatoid Arthritis
What happens to cloned B and T lymphocytes?
They survive long term as memory cells
What happens when a secondary exposure to the same antigen occurs?
The memory cells rapidly give rise to a new clone of specific lymphocytes which destroy the invading pathogens before the individual shows symptoms
What happens during the secondary response?
Antibody production is greater and more rapid than during the primary response
What does HIV do?
Attacks and destroys T lymphocytes
What does HIV cause?
The depletion of T lymphocytes which leads to the development of AIDS