phagocytosis Flashcards
(12 cards)
what is an antigen?
a protein on the cell surface membrane on a cell/pathogen that is identified as foreign because it is a different shape to ours, and therefore triggers an immune response
how do bacteria make us ill?
they release toxins
these toxins affect the way cells function i.e. make events happen that shouldn’t
these toxins damage cells i.e. cause cell death
how do viruses make us ill?
-infect your cells
-replicate within cells
-cause cell lysis
what type of immune system are phagocytes part of?
non-specific immune system (cells that respond to any foreign antigen)
where are pathogens most commonly found?
found in the blood and often at body surfaces such as the respiratory surface
what attracts pathogens to the site of infection?
chemotaxis occurs where chemicals released as the result of cell damage caused by pathogens attracts phagocytes there
what do the phagocytes already in the site of infection do? (2)
release cytokines that attract other phagocytes and other types of white blood cells called lymphocytes to the area
also release histamines which make capillaries more permeable so that other phagocytes and lymphocytes are able to leave capillaries and enter body tissue
what do phagocytes respond to and how?
to any cell with a foreign antigen( antigen that has different shape to those on body cells)
the phagocyte changes shape to flow around the pathogen or a virus infected cell and engulf it (virus infected cells present different antigens on surface)
where is the pathogen taken up into once engulfed? what happens here?
into a fluid filled sac called a phagosome
here lysosomes fuse with the phagosome and release hydrolytic enzymes (lysozymes)
hydrolysis reactions breakdown the large, insoluble molecules that make up the pathogen so that the pathogen is destroyed
the small, soluble molecules are taken up into the cytoplasm
after the pathogen has been killed via phagocytosis, what happens to the antigens?
they are presented in the cell membrane of the phagocyte to make what is called an antigen-presenting cell
what do the presented antigens on an APC enable?
the selection of the correct type of lymphocyte (T-cells and B-cells) required to destroy other pathogens of the same type that are present in the body
either through direct killing of a cell/ virus infected cell or through the production of specifically shaped antibodies
IT ENABLES THE STIMULATION OF THE SPECIFIC IMMUNE RESPONSE
describe the 6 steps of phagocytosis that is short enough for an exam answer?
-foreign antigen enters body
-phagocytes are stimulated by any foreign antigen
-phagocytes engulf the pathogen or cell that has foreign antigens into a phagosome
-lysosomes fuse with the phagosomes and release lysozymes
-these lysozymes catalyse the hydrolysis reactions that digest the pathogen or infected cell
-an antigen from the pathogen or infected cell is presented on the membrane of the phagocyte
