Unit 1 Immunity Flashcards
How does the body distinguish between its own cells and foreign ones?
Molecules on pathogens surface is identified as foreign, they activate the cells in the immune system. They are called antigens. (Usually proteins or polysaccharides)
What is the first line of defence against disease?
Phagocytosis
What is phagocytosis?
A phagocyte recognises an antigen on the pathogens surface
The cytoplasm of the phagocyte wraps its cytoplasm around the pathogen - engulfing it
Pathogen now in the cytoplasm of the phagocyte (phagocytic vacuole)
A lysosome fuses with phagocytic vacuole, lytic enzymes are released which break down the pathogen.
The phagocyte releases it and some of the antigens stick to its surface to activate other immune system cells.
What are antigens?
Proteins or polysaccharides on the surface of a pathogen which activate an immune response.
What are the two main types of lymphocytes?
T-lymphocytes
B-lymphocytes
What is the role of T-lymphocytes in cell-mediates immunity?
A T-cell has proteins on its surface which bind to the antigens presented by phagocytosis, this activates the T-cells. Some T-cells release substances to activate B-cells, others will attach to antigens on a pathogen and kill the cell.
What is the role of B-lymphocytes in humoral immunity?
(Type of white blood cell)
They are covered with antibodies which are proteins which bind to antigens to form antigen-antibody complex. Each B-cell has differently shaped antibodies on its membrane so different ones will bind to different shaped antigens. When antibody on surface meets a complementary shaped antigen it binds to it which helps to activate the B-cell. This activated B-cell divides and produces many more B-cells called plasma cells.
What are the roles of plasma cells and antibodies in the primary immune response?
Plasma cells are identical to the original B-cell (clones), they secrete loads of antibody specific to the antigen.
The antibodies functions are; to coat the pathogen to make phagocytosis easier, to coat the pathogen preventing it fro, entering host cells, binding to and neutralising toxins produced by the pathogen.
What is the role of memory cells in the secondary immune response?
If same pathogens enter the body again the immune system produces a quicker, stronger response (secondary response). Memory B-cells divide into plasma cells that produce the right antibody to antigen. Memory T-cells divide into the correct type of T-cells to kill the cell carrying the antigen. Secondary response often gets rid of the pathogen before you show any symptoms.
How does antigenic variation affect the body’s response to infection?
Some pathogens can change their surface antigens, so when you’re infected for a second time the memory cells produced from the first infection will not recognise the different antigens. The immune system has to carry out a primary response against the new antigens.
What is the structure of an antibody?
Antibodies are proteins, they are made from chains of amino acids linked together by peptide bonds. The specificity depends on its variable region (they also have a constant region - same for all antigens). Each antibody has a different shaped variable region that’s complementary to one specific antigen (due to its amino acid sequence). Also has heavy chains and light chains.
How to antibodies function?
They bind to specific antigens forming antibody-antigen complexes.
What is a monoclonal antibody and how are they produced?
Antibodies produced from a single group of genetically identical B-cells (plasma cells). You can make monoclonal antibodies that bind to anything you want, e.g. a cell antigen or another substance and they will only bind to this molecule.
Example - pregnancy tests
What is a vaccine?
Vaccines contained dead/weakened pathogens that cause your body to produce memory cells against the particular pathogen, without the pathogen causing disease. This means you become immune without getting any symptoms.
Vaccines protect people who have had the vaccine as reduce the occurrence of disease, also those who are not vaccinated are less likely to catch the disease - herd immunity (fewer people to catch it from).
What are the main defence mechanisms of the body?
