The specific immune response
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Why is a specific immune response necessary in the body?
If the pathogen has not been dealt with by the non-specific immune responses then it becomes important that the pathogen has s response which is specifically targeted against it. This takes the form of antibodies which are made for the shape of the antigens on the pathogen
Where are lymphocytes found?
In the lymphatic system as well as the blood stream
Where are T lymphocytes made and where do they mature?
-made in the bone marrow -mature in the thymus gland
What are T lymphocytes involved in?
Cell-mediated immunity
Where are B lymphocytes made and where do they mature?
Made and mature in the bone marrow
What are B lymphocytes involved in?
They make the antibodies and are involved in humoral immunity
What does the maturation process involve for both the T lymphocytes and the B lymphocytes?
-the development of the glycoprotein structures on the outside surface membrane -T cells= receptors -B cells= antibodies
What are the two different classes which T lymphocytes differentiate into in the thymus gland?
-T helper cells -T killer cells
What are T cells known as before they encounter the antigen to which they are complementary?
Naive
What is the third and fourth class of T lymphocyte?
T memory cells T regulatory cells
What are the functions of the T helper cells?
-they have CD4 receptors on their plasma membranes which bind to the surface of the antigens of APCs -they are activated by the cytokine Interleukin 1 (IL-1) produced by the APC -IL-1 causes T helper cells to undergo mitosis to produce more T helper cells -T helper cells produce the cytokine Interleukin 2 (IL-2) -They differentiate T memory cells and T regulatory cells
What does interleukin 2 do?
-activates B lymphocytes to bring about antibody production -stimulate T killer cells -Attracts and stimulates macrophages to ingest pathogens with antigen-antibody complexes
What is the function of T killer cells?
-Destroy the pathogen carrying the antigen -Produce a chemical called Perforin -Perforin makes holes in the plasma membrane of the pathogen -Also kills cells which have been infected with a virus -has CD8 receptors on its plasma membrane
What is the function of T memory cells?
-they are long lived -part of the immunological memory, which brings about a secondary response -if an antigen is encountered for a second time these cells divide rapidly to form huge numbers of clones of T killer cells
What is the function of T regulatory cells?
-suppress the immune system -once the pathogen has been eliminated these cells stop the immune response -this prevents the autoimmune responses -these are controlled by interleukins
What is the cell mediated immunity response for T lymphocytes?
-T lymphocytes respond to processed antigens- they do not respond directly with the pathogen itself but any cell of the host organism which displays processed antigens can activate T cells
Give examples of processed antigens which T lymphocytes will respond to.
-a macrophage which has done phagocytosis which is displaying the antigens on its plasma membrane -a cell infected with a virus - a cancer cell where a mutation has changed the cell -a transplanted organ
What does it mean when a T helper cell is naive?
These are T cells that have never been encountered with due to the many variations of shaped receptors on the plasma membrane.
What is the process of clonal selection?
-When a T helper cell encounters an antigen which is being displayed by an antigen presenting cell, it will bind to it. -these are specifically the T helper cell clones, with the specific shaped antigen-binding site, different from the others which are not a complementary fit
What happens when the T helper cell has bound to the presented antigen on the APC?
The APC release a type of cytokine called interleukin 1 to activate it
What is clonal expansion?
-When the T helper cell divides by mitosis to produce many T helper cells -T memory and T regulatory cells are also made -clonal= each of the daughter T helper cells have the same antigen specificity -expansion= result is a much larger number of clones of this variation of T helper cells are made
What is the humoral response for B lymphocytes?
-humor=body fluids -humoral response takes part in blood plasma and tissue fluid, as the B cells attack pathogens found outside the cells
Explain what B lymphocytes are covered with
-antibodies -these are proteins (immunoglobulins) which binds to antigens to form an antigen-antibody complex -there are many different versions of B cells, each with a different shaped antigen binding site which one will have a COMPLEMENTARY shape
Explain how B cells can undergo clonal selection
Only the B lymphocytes with the specifically shaped antigen binding site on its antibody will be able to bind to the antigen