T-cells and Immunity

AQA syllabus ... sbout T cells... :)

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T- Cells and Cell Mediated Immunity
The initial response is Phagocytosis (no specific) ... the next response is specifics... It confers immunity.
Immunity is the ability of micro-organism to resist infection by protecting against disease
causing micro-organisms.
Antigens are proteins on the cell surface membrane or the wall of the invading cell.
The antigen triggers an immune response
Antigens cause the production of antibodies.
Specific react to certain forms of infection Slower in action initially Provide long term
immunity Specific immune response depends on the type of lymphocyte.
B- lymphocytes humeral response to the antibodies that are present in the body's fluids
Responds to foreign material outside of cells Bacteria and viruses B-lymphocytes
Matures in the bone marrow
T-lymphocytes Cell mediated response inside the cell Immunity involving body cells
respond to foreign material inside of cells E.g. Cells that are affected b cancer or viruses,
or a response to a transplanted tissue. T lymphocytes mature in the thymus gland.
Cell mediated immunity
T-cells respond to the organelles own cell
When they have been invaded by a non-self material ­ e.g. A virus / cancer
They also respond to transplanted material which is genetically different
T-lymphocytes can distinguish between invader cells and normal cells
Phagocytes have engulfed and broken down the pathogen
Present some of the pathogen on its cell surface membrane
Body cells invaded with virus present some viral antigen on their cell surface membrane
Cancer cells present some of their antigens on their cell surface membrane
All these are therefore antigen presenting cells- as they present antigens from other cells.
1) Pathogens invade the body or are taken in by phagocytosis
2) The phagocyte places antigen from the pathogen on its cell surface membrane
3) Receptors on the T-cells fit exactly on to the antigen
4) This activated T-cells to divide rapidly and form a clone
5) The cloned T-cells ...
6) A) Develop as memory cells and therefore, provide rapid response to future infections.
B) Stimulates phagocytes to engulf pathogen by phagocytosis
C) Stimulates B-Cells to divide rapidly
D) Kills any infected cells
Receptors on T- cells are important
Receptors on each T-cell respond to a specific antigen
It follows that there are a vast number of T-cells
Each respond to a different antigen
How T-cells kill the perpetrator (infected cells) :p
T-cells kill body cells that are infected with pathogens
They kill by producing a protein which makes holes in the cell surface membrane of the cells

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This makes the cell freely permeable
As a result the cell dies
This just shows the importance of the cell surface membrane in maintaining the integrity of
the cell.
Action of T-cells is most effective on Viruses because they live inside the cell
As viruses need living organisms to reproduce
So a sacrifice of a few cells prevents the virus from multiplying and therefore, infecting other
cells.…read more


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