The specific immune response Flashcards
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
What are the B cells activated by?
Cytokines, (interleukins) released by the T helper cells
Explain how B cells can undergo clonal expansion
When the activated B lymphocyte then divides by mitosis into plasma cells and B memory cells
What is a blood smear?
A sample of blood smeared over a microscope slide, and stains are added to the sample to make the different cells easy to see.
What does identifying the numbers of different types of lymphocytes in a blood smear indicate?
If a non-specific or specific immune response is taking place
What is a differential white blood cell count?
Where you count the different types of white blood cells seen in the sample
What is a decrease in the number of leukocytes called?
Leukopenia
What is an increase in the number of leukocytes called?
Leukocytosis
How are antibodies produced?
Produced by plasma cells which are clones of the B lymphocyte, they have a binding site which is complementary to the antigen which caused the clonal selection and clonal expansion which led to the plasma cells being made
What organelles do plasma cells have lots of due to the mass production of antibodies ?
Ribosomes, RER, golgi, secretory vesicles to enable a high rate of protein synthesis
How are antigen-antibody complexes made and what is their function?
-When antibodies bind to the antigens on the surface of the pathogen
-this targets the pathogen for the phagocytes, and is when antibodies act as opsonins
Describe and explain the structure of antibodies
-the variable region of the antibody forms the antigen binding site
-shape of variable is complementary to a particular antigen
-the variable region differs between antibodies from other B cells which are not complementary to the antigen
-hinge region which allows flexibility when the antibody binds to the antigen
-the constant region is the same in all antibodies= allows binding to receptors on immune system cells
-polypeptide chain of protein structure are held together by disulphide bonds
What is the first role of antibodies in clearing infections?
- Agglutinating pathogens
-each antibody has 2 binding sites so can bind to two pathogens at the same time, so they become clumped together
What is the second role of antibodies in clearing infections?
- Neutralising toxins
-Antibodies called anti toxins can bind to the toxins produced by pathogens. This prevents the toxins from affecting human cells, so the toxins are neutralised
What is the third role of antibodies in clearing infections?
- Preventing the pathogen binding to human cells
-when antibodies bind to the antigens on pathogens, they make block the cell-surface receptors that the pathogen needs to bind to the host cell.
