T5: Cell recognition& the immune system Flashcards
What are antigens?
-molecules (usually proteins) located on the surface of cells
-generate an immune response when foreign antigens detected
What can antigens identify ?
-pathogens (foreign antigens on its surface generate immune response)
-abnormal body cells(abnormal antigens generate immune response)
-toxins/poisonous molecules (no antigens ,immune system responds to the pathogen that releases them)
-Cells from other individuals of the same species (foreign antigens trigger an immune response, can be suppressed0#
What blood type is the universal recipient?
-Type AB
-has no antibodys and A+B antigens
What blood type is the universal donor?
-Type O
-neither A or B antigen
-both A +B antibody so can only get type O blood
What happens in Phagocytosis (stage 1 of immune response?
-phagocyte engulfs pathogen by:
-recognises the foreign antigens on a pathogen
-cytoplasm moves round pathogen to engulf
- pathogen contained in phagocytic vacuole
-lysosome fuses with phagocytic vacuole and lysozymes break down pathogen
-phagocyte then acts as an antigen-presenting cell
What is a T-cell?
-T-lymphocyte is a type of WBC
-receptor proteins on its surface that bind to complementary antigens on phagocytes
-receptors on T-cells respond to a single antigen
-Tcells react in different ways
What do helper T-cells do?
-receptors on the TH cells bind to the specific antigens
-they divide rapidly by mitosis
-activate b-cells
What do cytotoxic T-cells do?
-kill abnormal and foreign cells
-producing perforin (protein) that makes holes in the cell-surface membrane
-pathogen becomes freely permeable to all substances and the cell dies as a result
What do B-lymphocytes do?
-humoral immunnity
-covered in antibodies
-clonal selection
-b-cells divide into plasma
What are monoclonal antibodies ?
-B-cell clones which produces its own antibody
-PLASMA CELLS: primary immune response which sucrete antibodies into plasma
-MEMORY CELLS: secondary immune response which circulate blood and tissue fluid for years
What are memory cells?
-responsible for the secondary immune response
-live long
-do not produce antibodies directly, but circulate the blood and tissue fluid
-when encountering the same antigen at a later date, they rapidly divide and develop into plasma cells and more memory cells
What is the cellular response?
-T-cells and other immune system cells that they interact with form cellular response
What is humoral immunity?
-involves antibodies (soluble in blood and tissue fluid ‘4humors’)
-Bcells produce specific antibody
What is clonal selection?
-Helper t cells bind to antigen presenting cells
-stimulates Bcells to divide by mitosis forming clones with specific antibodies
What is cell mediated immunity/ cell response?
-T-lymphocytes responding to antigens on presented on a body cell
What is a phagosome?
-vesicle formed when a phagocyte engulfs a pathogenic microorganism
What is an antibody ?
-protein produced by a B lymphocyte/ B plasma cell in response to the presence of a foreign antigen
What is the structure of an antibody?
-4 polypeptide chains- they have a pair of heavy chains (longer) and a pair of light chains (shorter)
-variable region-binding site that fits very precisely onto a specific antigen to form an antigen-antibody complex
-constant region- this binds to receptors on cells such as B cells
-hinge region gives the antibody stability
How can anti-cancer drugs target cancer cells?
-Cancer cells have antigens called tumour markers
-Monoclonal antibodies made to bind to tumour markers
-attach anti-cancer drugs to the antibodies(drug will accumulate where cancer is)
What are ethical issues with monoclonal antibodies?
-involve animal rights issues
-animals (often mice) used to produce the cells from which the monoclonal antibodies are produced
What is ELISA Test ?
-enzyme-linked immunosorbent assay
-see if a patient has antibodies to a certain antigen
-used in medical diagnosis to test for pathogenic infections & allergies
How does an ELISA work?
-antibody with enzyme attached can reacts with substrate to form colour
-colour change, it shows presence of antigen or antibody of interest
What is direct ELISA?
-patients antigens bound to well
-detection antibody (with an attached enzyme) that is complementary to the antigen of interest is added
-antigen is present in the sample, it will be immobilised on well and detection antibody will bind to it
-rinse to remove unbound antibodies
-substrate solution is added ,colour change- positive result of the antigen
