the immune system (immune response) Flashcards
what is an antigen?
protein that can generate an immune response
what are antigens used by the immune system to identify?
pathogens
abnormal body cells, eg cancer cells
toxins
cells from other individuals of the same species eg,organ transplants
what is a pathogen?
organism that causes disease
what are the 4 stages of the immune response?
phagocytes engulf pathogens
phagocytes activate T cells
T cells activate B cells which divide into plasma cells
plasma cells make more antibodies to a specific antigen
what happens in phagocytosis?
phagocyte recognises foreign antigens on a pathogen
cytoplasm engulfs the pathogen
phagocyte contained in a phagocytic vacuole
lysosome fuses with the phagocytic vacuole
lysozymes break down the pathogen
phagocyte presents the pathogen’s antigen on its surface to activate other immune cells
what happens when phagocytes activate T cells?
helper T cells release chemical signals that activate/stimulate phagocytes
cytotoxic T cells kill abnormal and foreign cells
activate B cells which secrete antibodies
what is a T cell?
type of white blood cell with receptors on its surface that bind to the complementary antigens presented by phagocytes
what is a B cell?
type of white blood cell, covered with antibodies
what is an antibody?
protein that binds antigens
what happens when B cells meet an antigen?
when the antibody on a B cell surface meets a complementary antigen, it binds to it
this activates the B cell (clonal selection)
activated B cell divides into plasma cells
what are plasma cells?
cell that are clones of B cells
what do plasma cells do?
secrete monoclonal antibodies, which are specific to the antigen
what happens when antibodies bind to antigens on the surface of the pathogen?
forms an antigen-antibody complex
why does an antibody have two binding sites?
can bind to 2 pathogens at the same time
pathogens become clumped together=agglutination
phagocytes bind to antibodies and phagocytose many pathogens at once
why is an antibody specific?
has variable regions which make up the antigen binding sites
have a unique tertiary structure
what is the cellular immune response?
T cells and other immune system cells that they interact with
what is the humoral immune response?
B cells, clonal selection and the production of monoclonal antibodies
what is the primary immune response?
when an antigen enters the body for the first time
what happens in the primary immune response?
slow as there aren’t many B cells
infected person shows symptoms whilst producing the antibody
after exposure, T and B cells produce memory cells so the person is immune
what is the role of a memory T cell?
remember the specific antigen and will recognise if it enters the body again
what is the role of a memory B cell?
records the specific antibodies needed to bind the antigen
what is the secondary immune response?
when the same pathogen happens again
what happens in the secondary immune response?
clonal selection occurs faster
memory B cells activated and divide into plasma cells
memory T cells are activated and divide into the correct type of T cells
rid of pathogen before symptoms
