Cell recognition and the immune system (Chapter 5) Flashcards
What are pathogens?
Micro organisms that cause disease, damage cells/tissue and produce toxins.
Describe how lymphocytes recognise your own cells
There are proteins on the surface of cells which can distinguish between cells and are individual to each person.
Describe phagocytosis
1) Phagocyte is attracted to bacteria by chemicals or recognise antigens on bacteria as foreign.
2) Phagocytes attach to chemicals on pathogens.
3) Engulf bacteria.
4) Bacteria is held in vacuole/vesicle/phagosome.
5) A lysosome fuses with vacuole or empties lysozymes into it.
6) Bacteria is digested or hydrolysed.
Describe T-Cells
Mature in the thymus and are associated with cell mediated immunity.
Describe B-Cells
Mature in bone marrow and are associated with antibodies/humoral immunity (memory or plasma cells). Memory cells carry an immunological memory of the specific antigen. Plasma cells produce antibodies.
Describe cell mediated immunity
1) Pathogens contain antigens on the surface.
2) Pathogen taken up by phagocyte and antigen presented on the surface.
3) Binds with the receptor on specific T helper cell.
4) This activates other t-cells by releasing chemical signals (cytokines)
5) Divides by mitosis to form clones.
6) Cloned t-cells stimulate phagocytes to engulf pathogens by phagocytosis.
7) B-cells are stimulated to divide into memory and plasma cells by mitosis.
8) Stimulates cytotoxic t-cells to divide and kill infected cells.
What are antibodies?
Proteins which are specific/complementary shape to antigen due to tertiary structure and destroy pathogens.
What is agglutination?
Clumps of bacteria cells which are formed making it easier for the phagocytes to locate them.
What do markers do?
Stimulate phagocytes to engulf the bacterial cells to which antibodies are attracted to.
Describe humoral response
1) B-cell can be antigen presenting cells or can bind to antigen or be presented on phagocyte.
2) Once the b-cell has processed the antigen or bound to it, it is then activated by t-helper cells.
3) B-cells now divide by mitosis to form a clone of identical b-cells.
4) Cloned plasma cells secrete antibodies.
5) Some B cells develop into memory cells and they can divide rapidly and develop into plasma cells that produce specific antibodies in response to future infections (secondary immune response).
What are monoclonal antibodies?
Antibodies made from single clone of B cells used on things such as pregnancy tests, medication and medical diagnosis.
What are antigens?
Foreign protein on cell surface that stimulates an immune response.
What is herd immunity?
When 95% of the population are vaccinated so most people are immune so there is little chance of contact with infected people.
Describe how vaccines work?
1) Contain antigens which are injected into the body.
2) Antigens on pathogens surface bind to receptor on t-helper cell.
3) T-cells release cytokines.
4) Stimulates B-cells to divide by mitosis to form clone of identical B-cell.
5) Plasma cells from B-cells make antibodies.
6) Some B-cells become memory cells.
7) On secondary exposure, memory cells produce antibodies rapidly.
What are the roles of antibodies in an ELISA test?
1) First antibody binds/attaches/complementary in shape to antigen.
2) Second antibody with enzyme attached is added.
3) Second antibody attaches to antigen.
4) Substrate or solution is added and colour changes.
