immunity Flashcards
what is a pathogen
communicable diseases that are caused by microoragnisms.
how many types of pathogens are there
-Bacteria - Produce toxins that damage body cells.
-Viruses - Use host cells to replicate before bursting out and destroying cells.
-Protoctists - Take over cells and break them open.
-Fungi - Digest living cells to destroy them and some produce toxins.
what is an antigen
a protein molecule capable of causing an immune response.
does every cell contain an antigen on its cell surface membrane
yes
where can antigen be found
As toxins, On the surface of pathogens
what are whiteblood cells
protect body from any diseases-phagocytes and lymphocytes
when does lymphocytes start to differentiate body cell antigen and pathogen antigens
Lymphocytes are exposed to self antigens while the baby is still in the uterus.
what does the defense mechanism consist of
specific and non specific
what is specific response
much slower response and is specific for one pathogen eg. humoural response- B lymphocyte and cell mediated response- T lymphocyte
what is a non specific
immediate- same for all pathogens eg.physical barrier-skin and phagocytosis
what is phagocytes
a non specific response- type of white blood cell that engulfs and destroys pathogens
explain role of phagocytosis
1.the phagocyte is attracted to the chemotaxis chemicals released by the pathogen and moves towards it along a conc gradient. 2. the phagocyte receptors attach to the chemicals and i engulfs it by endocytosis and forms a phagosome. 3. the lysosome fuses with phagosome and releases hydrolytic digestive enzymes-digest the pathogen using hydrolysis reaction 5. phagocyte absorbs any useful products of digestion into its cytoplasm.
how many types of lymphocyte cells are there
2- T cells and B cells
what are t cells
mature in the thymus glands and bring about a cellular
response to infection. They do not produce antibodies. responds to foreign material inside body cells.
what are B cells
mature in the bone marrow and release many antibodies
(a humoral response). respond to foreign material outside body cells eg. bacteria and virus
how many types of t cells are there
3- helper t cell, memory t cell, cytotoxic t cell
explain the role of t lymphocytes
1.Phagocytes engulf pathogens and display their antigens on the cell-surface. They are now known as antigen-presenting cells.
2.Receptors on a specific T helper cell fit exactly onto these antigens and bind to
them. Known as clonal selection
3. This binding activates the T cell to divide rapidly by mitosis and form a clone of
genetically identical cells (clonal expansion)
what are the function of the cloned t cells
Stimulate phagocytosis - Cloned cells stimulate phagocytes to engulf pathogens.
Develop into memory cells - These circulate in the body to provide long-term immunity.
Stimulate division of B cells - Cloned cells stimulate B cells to divide and produce antibodies.
Activate cytotoxic T cells - This allows TC cells to kill infected cells.
explain the humoral response
1.A B cell with a complementary antibody binds to the antigens on a pathogen.
2. The B cell engulfs the pathogen and presents its antigens on the cell-surface membrane to become an antigen-presenting cell.
3. Clonal selection - Activated T helper cells bind to the B cell, causing activation of this B cell.
4. Clonal expansion - The activated B cell divides by mitosis to form plasma and memory cell clones.
5.The cloned plasma cells produce and secrete the specific antibody which is complementary to the antigen on the pathogen’s surface. These antibodies attach to antigens on pathogens and destroy them.
6. The memory cells circulate the blood and tissue fluid, ready to divide if the body is re-infected by the same pathogen
