topic 2 - the immune system Flashcards
cgp (topic 2C) 46 - 47
what triggers an immune response
foreign antigens
what are antigens
marker molecules (usually proteins) present on the surface of cells that can generate an immune response when detected by the body
what are antigens used by the immune system to identify
(1) pathogens
(2) abnormal body cells
(3) toxins/ cells from other individuals of the same species
what are the four main stages in the immune response
(1) phagocytes engulf pathogens
(2) phagocytes activate t-cells
(3) t-cells activate b-cells, which divide into plasma cells
(4) plasma cells make more antibodies to a specific antigen
what is a phagocyte
a type of blood cell that carries out phagocytosis
what is phagocytosis
the process by which a cell uses its plasma membrane to engulf pathogens
where are phagocytes found
in the blood and in tissues and are the first cells to respond to an immune system trigger inside the body
what’s an example of a phagocyte
macrophage
what is the first step to a phagocyte engulfing a pathogen
a phagocyte recognises the foreign antigens on a pathogen
what is the second step to a phagocyte engulfing a pathogen
the cytoplasm of the phagocyte moves round the pathogen, engulfing it
what is the third step to a phagocyte engulfing a pathogen
the pathogen is now contained in a phagocytic vacuole (a bubble) in the cytoplasm of the phagocyte
what is the fourth step to a phagocyte engulfing a pathogen
a lysosome (an organelle that contain enzymes called lysozymes) fuses with the phagocytic vacuole - the lysozymes break down the pathogen
what is the fifth step to a phagocyte engulfing a pathogen
the phagocyte then presents the pathogen’s antigens - it sticks the antigens on its surface to activate other immune system cells
what is a t-cell
otherwise known as a t-lymphocyte is a type of white blood cell
what activates the t-cell
when its receptor proteins on its surface bind to complementary antigens presented to it by pathogens
different t-cells respond in different ways, give an example
helper t-cells (tH cells) release chemical signals that activate and stimulate phagocytes and cytotoxic t-cells (tc cells), which kill abnormal and foreign cells
what are the two main types of t-cells
(1) cytotoxic t-cells which destroy infected cells
(2) helper t-cells which send signals that direct other immune cells to fight infection
what is a b-cell
otherwise known as b-lymphocytes is a type of white blood cell that is covered in antibodies which originates and matures in bone marrow
why do different b-cells bind to different shaped antigens
because each b-cell has a different shaped antibody on its membrane
what are the three steps to how b-cells divide into plasma cells
(1) when the antibody on the surface of a b-cell meets a complementary shaped antigen, it binds to it
(2) this, together with substances released from helper t-cells, activates the b-cell - this process is called clonal selection
(3) the activated b-cell divides into plasma cells
what other cell is identical to b-cells
plasma cells
what are monoclonal antibodies
antibodies specific to the antigen which are secreted by a single clone of a specific white blood cell (plasma cells)
what do monoclonal antibodies bind to, what does this form
they bind to antigens on the surface of the pathogen to form lots of antigen-antibody complexes
name seven structures on the antigen-antibody complex
(1) antigen
(2) variable regions
(3) hinge protein
(4) constant regions
(5) light chain
(6) disulfide bridges
(7) heavy chain
