Specific cellular defences against pathogens Flashcards
Where are lymphocytes derived
lymphocytes are derived from tissue stem cells in the bone marrow
What do lymphocytes respond to
Specific antigens on invading pathogens
How do lymphocytes recognise specific antigens
lymphocytes have a single type of membrane receptor specific to one antigen
What happens when the membrane receptor is activated by the binding of an antigen
the lymphocytes repeatedly divide resulting in a clonal population of identical lymphocytes
How do B- lymphocytes help in defence
each B lymphocyte clone produces a specific antibody molecule that will recognise a specific antigen surface molecule on a pathogen or a toxin
What is an antibody
antibodies are Y-shaped proteins that have receptor binding sites specific to a particular antigen on a pathogen
How does the antigen-antibody complexes render the pathogen harmless
antibodies inactivate the pathogen making the antigen-antibody complex more susceptible to phagocytosis
What is an allergy
allergy is a hypersensitive b lymphocyte response to an antigen that is normally harmless
How do t lymphocyte recognise a pathogen
by recognising antigens of the pathogen on the cell membrane of infected cells
What is the role of T lymphocytes
To destroy infected cells by inducing apoptosis (programmed cell death)
What is apoptosis
programmed cell death
Why don’t T lymphocytes attack our own body cells
T- lymphocytes can normally distinguish between self antigens on the bodys own cells and non self antigens on infected cells
What is autoimmune disease
When the immune system regulation fails and leads to T-lymphocytes attacking self antigens on cells
An exposure to the same antigen will bring about a secondary response what is this secondary response
The memory cells rapidly produce a new clone of specific lymphocytes
Describe the role of memory cells in the immune system
to respond quickly to another invasion of a pathogen with the same antigen
What is the primary response
when a person is infected by a pathogen, b lymphocytes responds by producing antibodies. this takes time and the person usually suffers from the disease
What happens during the secondary response
antibodies are produced faster
more antibodies are produced than during the primary response
the antibody concentration remains high for longer
What does HIV stand for
human immunodeficiency virus
What does aids stand for
Acquired immune deficiency syndrome
How does HIV attack the immune system
HIV attacks and destroys T lymphocytes reducing their numbers
this can lead to the development of AIDS
What are the consequences of developing AIDS
because the person has less T lymphocytes they become more susceptible to opportunistic infections
How is HIV transmitted from person to person
exchange of body fluids
Describe T lymphocytes and porteins
T lymphocytes attach on to infected cells and release proteins
these proteins diffuse into the infected cells causing a production of self destructive enzymes which causes cell death
the remains of the cell are then removed by phagocytosis
What name is given to molecules located on the surface of cells that trigger a specific immune response
antigen
Explain how a lymphocyte is able to recognise a particular
pathogen.
it recognises an antigen
Explain how a clonal population of lymphocytes would be formed
when a pathogen invades the body.
The receptors on the lymphocyte
bind to the antigen
this leads to lymphocytes rapidly dividing resulting in a clonal population of identical lymphocytes
Describe the role of phagocytes in the specific immune response.
phagocytes engulf pathogens
These cause the production of
T-lymphocytes.
