Unit 3-Specific Cellular Defences Against Pathogens Flashcards
What is the specific immune response brought about by?
White blood cells called lymphocytes.
Where are lymphocytes produced?
From stem cells in the bone marrow.
What are the two types of lymphocytes?
B and T lymphocytes
What are T lymphocytes?
Lymphocytes that pass into the thymus where they develop into T lymphocytes.
What are B lymphocytes?
Lymphocytes that remain in the bone marrow an become B lymphocytes.
What do lymphocytes respond to?
Specific antigens on invading pathogens.
What is an antigen?
A molecule (often a protein) found on the surface of cells.
What are the 2 types of antigen?
Self antigens (belong to the body’s own cells) and foreign antigens (do not belong to the body’s own cells).
What do foreign antigens do?
Trigger a specific immune response.
What do lymphocytes have in terms of antigens?
Lymphocytes have a single type of antigen receptor which is specific for one antigen.
After foreign antigen binding what does the lymphocyte do?
The lymphocyte divides repeatedly, resulting in the formation of a clonal population of identical lymphocytes.
What do B lymphocytes do?
Produce antibodies against antigens and this leads to destruction of a pathogen.
What are antibodies?
Y-shaped protein with receptor binding sites that are specific to a particular antigen on a pathogen.
What do antibodies do?
Antibodies bind to their specific antigens which are on the surface/membrane of the pathogen. The resulting antigen-antibody complex can then be destroyed by a phagocyte.
What does an allergic reaction happen?
When B lymphocytes respond to antigens on substances that are harmless to the body, e.g. pollen. This hypersensitive response is called an allergic reaction.
What are examples of allergic reactions?
Hayfever and peanuts.
Which type of lymphocytes produce antibodies?
B lymphocytes
What do T lymphocytes do?
Destroy infected body cells by recognising antigens on the pathogen on the cell surface.
How do T lymphocytes destroy infected body cells?
They attach onto the infected cells and release proteins. These proteins diffuse into the infected cells causing production of self-destructive toxic chemicals which cause cell death.
How are remaining cells of destruction of infected cells by a T lymphocyte removed?
By phagocytes
What is apoptosis and what is an example of this?
Programmed cell death, like T lymphocytes.
What can T lymphocytes normally distinguish between?
Self antigens on the body’s own cells and non-self antigens on infected cells.
What does failure of the regulation of the immune system lead to?
T lymphocytes responding to self antigens.
What happens when T lymphocytes respond to self antigens?
T lymphocytes attack the body’s own cells causing autoimmune disease such as type 1 diabeties and rheumatoid arthritis.
What are disease caused by the failure of the regulation of the immune system where T lymphocytes attack the body’s own cells?
Type 1 diabetes and rheumatoid arthritis.
What do some B and T lymphocytes produced in the response to antigens do?
Survive long term as memory cells.
How do memory cells work?
When the body is exposed to the same antigen for a second time the memory cells quickly give rise to a new clone of specific lymphocytes, which destroy the invading pathogens before an individual shows symptoms.
How does secondary response due to memory cells usually prevent diseases?
Antibody production is rapid and more effective than during the primary response.
What does HIV stand for?
The human immunodeficiency virus.
How does HIV work?
The HIV attacks and destroys T lymphocytes causing depletion of T lymphocytes which leads to the development of AIDS.
What does AIDS stand for?
Acquired Immune Deficiency Syndrome
What are the characteristics of someone with AIDS?
They have a weakened immune system and so are vulnerable to opportunistic infections.
What does autoimmunity mean?
When the T lymphocytes attack the own body’s cells.
Why does someone not experience symptoms if exposed to an antigen a second time?
The response of antibodies is more rapid and effective.
