immune system Flashcards
what is a pathogen?
a microorganism that causes disease
what is immunity?
the body’s ability to kill a pathogen before it causes any harm
what are the 2 types of white blood cell?
lymphocyte and phagocyte
what are the two types of lymphocyte?
T-Lymphocyte and B-Lymphocyte
why must white blood cells be able to distinguish between cell and non-self?
this allows the white blood cells to know what is part of your body, and what is not so that the body’s own tissues aren’t destroyed
what is used to identify cells as self or non-self?
the proteins on the cell surface
why are proteins used to identify whether cells are self or non-self?
they have a huge variability and the 3D (tertiary) structure is very specific
what is the immune system able to identify?
- pathogens (e.g. HIV)
- non-self material (e.g. cells from another organism)
- toxins
- abnormal body cells (e.g. cancer)
what is the name given to the protein which causes an immune response?
antigens
what issue may arise with the immune system, due to transplants?
the immune system may recognise the tissues as non-self, and therefore attack transplanted organs/tissues.
2 types of defense
specific and non-specific
2 types of non-specific defense
physical barrier and phagocytosis
2 types of specific defense
cell mediated response and humoral response
what type of cells are involved in cell-mediated response?
t-lympocytes
what type of cells are involved in humoral response?
b-lymphocytes
when a pathogen enters the body, how is the correct lymphocyte selected?
it already exists in the body, but must be stimulated to replicate
what do we mean by “correct” lymphocyte for a particular pathogen?
just as each pathogen has specific proteins on their surface that indicated what they are. the lymphocytes have complementary proteins which fit those of the pathogen
phagocytosis
engulfment of pathogens
phagocytosis (process)
- phagocyte recognises foreign antigens on the pathogen
- cytoplasm of the phagocyte moves around the pathogen, engulfing it
- the pathogen is now contained in a phagocytic vacuole
- a lysosome fuses with the phagosome and the lysozymes break down the pathogen
- the phagocyte presents the pathogen’s antigens-> it sticks the antigens on its surface to activate other immune system cells
t-cells/t-lymphocytes
another type of white blood cell; activated by phagocytes;
has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes, which activates the t-cell;
helper t-cells release chemical signals that activate and stimulate phagocytes and cytotoxic t-cells which kill abnormal and foreign cells;
also activate B-cells which secrete antibodies
b-cells/b-lymphocytes
another type of white blood cell; activated by T-cells;
covered in antibodies – proteins that bind with antigens to form an antigen-antibody complex;
each B-cell has a different shaped antibody on its membrane, so different B-cells bind to different antigens;
when the antibody on the surface of a B-cell meets a complementary shaped antigen, it binds to it;
this, together with chemical signals released by helper T-cells, activates the B-cell (clonal selection); activated B-cell divides into plasma cells
plasma cells
identical to B-cells (clones);
they secrete loads of antibodies specific to the antigen – monoclonal antibodies – which bind to the antigens on the surface of the pathogen to form antigen-antibody complexes
antibodies
proteins – made up of chains of amino acids;
the specificity of an antibody depends on its variable region (binding site);
each variable region has a unique tertiary structure that is complementary to one specific antigen; antibodies have two binding sites – it can bind to two pathogens at the same time;
this means pathogens become clumped together – agglutination;
phagocytes then bind to the antibodies and phagocytose many pathogens all at once; this process leads to the destruction of pathogens carrying this antigen in the body
phagocytes
patrol the body, searching for invaders (non-self antigens);
ingest and destroy pathogens in phagocytosis
when the pathogen is engulfed, what is the vesicle called?
phagosome
what fuses with the phagosome?
lysosomes