Lymphoctyes and the Immune Response Flashcards
Where do B lymphocytes mature
Bone marrow
Where do T lymphocytes mature
Thymus gland
Types of T lymphocytes
T killer
T helper
T memory
T regulator
T helper cells
- CD4 receptors on their cell surface membrane which bind to the surface antigens on APCs
- produce interleukins ( type of cytokine - cell signalling molecule )
- interleukins made by the T helper cells stimulate the activity on the B cells which increases antibody production , stimulates production of other types of T cells and attracts & stimulate macrophages to ingest pathogens with antigen- antibody complexes
T killer cells
- destroy the pathogen carrying the antigen
- produce a chemical called perforin
- which kills the pathogen by making holes in the cell membrane so it is freely permeable
T memory cells
- live for a long time
- apart of immunological memory
- if they meet a antigen a second time they divide rapidly to form many clones of T killer cells that destroy the pathogen
T regulator cells
- cells suppress the immune system acting to control and regulate it
- stop the immune response once a pathogen has been eliminated
- make sure the body recognises self antigens and does not set up an autoimmune response
- interleukins are important in this control
Main types of B lymphocytes
- plasma cells
- B effector cells
- B memory cells
Plasma cells
- produce antibodies to a particular antigen and release them into the circulation
- an active plasma cell only lives for a few days but produces around 2000 antibodies per second while it is alive and active
B effector cells
These divide to form the plasma cell clones
B memory cells
- live for a long time and provide immunological memory
- they are programmed to remember a specific antigen and enable the body to make a very rapid response when a pathogen carrying that antigen is encountered again
Cell mediated immunity
T lymphocytes respond to the cells of an organism that have been changed in some way for eg. By a virus infection, by antigen processing or by mutation
Non specific defence system
- Macrophages engulf and digest pathogens in phagocytosis
- process antigens from the surface of the pathogen to form antigen presenting cells ( APCs) - Receptors on some of the T helper cells fit the antigens
- these T helper cells become activated and produce interleukins which stimulate more T cells to divide rapidly by mitosis
- they form clones of identical activated T helper cells that all carry the right antigen to bind to a particular pathogen
The cloned T cells may :
- develop into T memory cells which give a rapid response if this pathogen invades the body again
- produce interleukins that stimulate phagocytosis
- produce interleukins that stimulate B cells to divide
- stimulate the development of a clone of T killer cells that are specific for the presented antigen and then destory infected cells
Humoral immunity
Body responds to antigens found outside the cells for eg. Bacteria and fungi
What does humoral immunity produce ?
Antibodies that are soluble in the blood and tissue fluid and are not attached to cells
Clonal expansion & selection
- Activated T helper cells bind to the B cell APC ( clonal selection )
- the point at which the B cell with the correct antibody to overcome a particular antigen is selected for cloning - Interleukins produced by the activated T helper cells activate the B cells
- The activated B cell divides by mitosis to give clones of plasma cells and B memory cells ( clonal expansion )
Autoimmune disease
The immune system stops recognising self cells and starts to attack healthy body tissue
Autoimmune disease examples
- type 1 diabetes
- rheumatoid arthritis
- lupus
