IMMUNITY Flashcards
1st line of defence
skin saliva mucus tears (lysozyme break down bacterial cell walls) blood clotting epithelia stomach acid
antigen
a substance that is foreign to the body and stimulates an immune response.
may be glycolipids, proteins, lipids, polysaccharides and waste material
immune response
a complex series of responses of the body to the entry of a foreign antigen, involving lymphocytes and phagocytes.
2 types of white blood cell
phagocytes
lymphocytes
where are phagocytes produced?
in the bone marrow before later being distributed throughout body
2 types of phagocytes
neutrophils
macrophages
neutrophils
leave capillaries via squeezing through small spaces to patrol tissues, released in large numbers during infection and last about 2 days.
macrophages
produced as monocytes in bone marrow to travel in the blood before settling as macrophages in the organs.
remove foreign matter from organs and last longer than neutrophils, cutting up pathogens to display to lymphocytes on membrane.
antigen-presenting cell
how do neutrophils know which invading pathogens to destroy
invading pathogens cause release of histamines which attract neutrophils via chemotaxis so that they can destroy pathogens via phagocytosis
phagocytosis process
cell surface membrane of neutrophil engulfs pathogen in a vesicle via endocytosis, fusing w a lysosome which releases digestive enzymes, destroying the pathogen
lymphocytes types
T lymphocytes
B lymphocytes
where are lymphocytes produced
in the bone marrow
circulate between blood and lymph nodes
T lymphocytes location
bone marrow before moving to thymus in chest (shrinks over puberty)
B lymphocytes location
in the bone marrow before maturing enough to spread throughout the body into the lymph nodes and spleen.
antibody
A glycoprotein (immunoglobulin) made by plasma cells derived from B lymphocytes, secreted in response to an antigen; the variable region of which is complimentary to the antigen.
B lymphocytes role
as mature, develop ability to produce antibodies against pathogens/ particular antigens.
these antibodies stay embedded in the cell surface membrane to form a glycoprotein receptor, which specifically combines with one type of antigen.
T lymphocytes role
have specific T cell receptors on surface of similar structure to antibodies, specific to each antigen.
when are t lymphocytes activated
when they encounter the antigen engulfed by a macrophage and displayed on its surface
2 types of T lymphocytes
killer T cells (cytotoxic)
helper T cells
killer T cells role
search for invaded cells w foreign antigens from pathogens, secreting toxic substances to kill it.
helper T cells
release cytokines upon activation which stimulates B cell division, plasma cell development, antibody secretion or macrophage speeding up.
process by which killer T cells kill pathogens
T cells bind to the infected cell w T cell receptor complimentary to antigen.
perforin forms holes in the cell membrane so that enzyme enters which promotes apoptosis
non-self
a substance or cell that is recognised as foreign by immune system, triggering an immune response.
self
substance produced by the body that the immune system doesn’t recognise as foreign.
MHC
Major Histocompatibility Complex
major histocompatibility complex
specific glycoproteins that are specific to each cell, coded by genes on chromosome 6 (genetically determined).
Why are some lymphocytes destroyed in the thymus upon maturation?
because originally, every possible structure of lymphocyte is made, meaning lymphocytes which recognise self antigens as foreign must be destroyed (if not, leads to autoimmune disease)
How do B cells identify the antigen
they line up to the macrophage to see whether any of the antigens are complimentary to the antibodies and so can bind to it, ingesting the antigen via endocytosis and displaying them on the surface membrane
How are B cells activated?
the T cells bind to the surface antigens of the B cells of the same antigen, activating the B lymphocyte to divide rapidly via mitosis to form a mass of cloned cells (plasma cells) full of RER to mass produce antibodies.
how are antibodies released into the bloodstream?
they are released via exocytosis and pass into the blood stream and tissue fluid to overwhelm the pathogen.
clonal selection
process by which a singular B or T cell recognising an antigen is selected from the pre-existing pool of differing cell specificities.
clonal expansion
when many copies of the B cell are produced to form a mass of plasma cells.
what happens to the antibodies and B and T cells after the pathogen has been destroyed?
they disappear from the bloodstream
except that of retained lymphocytes that act as memory cells.
cell mediated response
going directly to the site rather than secreting antibodies (killer T cells)
humoral response
producing antibodies which travel via bodily fluids to do the work.
2 groups of stem cells in the bone marrow
myeloid and lymphoid
myeloid stem cells
produce neutrophils, monocytes and platelets.
lymphoid stem cells
produce b and t lymphocytes
leukaemia
cancer of the lymphoid cells, producing many non-differentiating cells that disrupt normal blood production.
body lacks red blood cells and platelets needed, leading to excessive bleeding and anaemia, as well as immunosuppression.
acute
developing suddenly and requiring immediate treatment
chronic
developing slowly and monitored as to when to give treatment
antibodies
globular glycoproteins with a quarternary structure, forming a group of plasma proteins known as immunoglobulins
structure of antibodies
2 long/heavy chains and 2 short/light chains connected via strong disulphide bridges
why are antibodies so specific
the sequences of amino acids in the binding sites gives them their specificity to a singular antigen, known as the variable region
hinge region function
donates flexible properties so that it can bind to the antigen more easily
heavy chain function
can be recognised by phagocytes which engulf any pathogen w the antibody attached
antitoxins
antibodies counteracting toxins
autoimmune disease
when the immune system turns on its host and attacks own body cells
how do autoimmune diseases come about
Immune cells that should have been destroyed by the thymus have been retained, meaning that they can be activated and produce an immune response to self antigens (localised or whole body)
active immunity
acquiring an infection and mounting an immune response via production of antibodies against the pathogen as well as memory cells
artificial active immunity
stimulation of the immune system
