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MIBO EXAM 5 WITH 100% CORRECT ANSWERS
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MIBO EXAM 5 WITH 100% CORRECTANSWERS
Secretory IgA is found in the secretions that coat mucus membranes, thereby preventing
pathogens from colonizing mucosal surfaces. What are methods that bacteria have evolved to
evade or inactivate these antibodies?
-IgA proteases that cleaves the antibodies, so that they cannot bind to the pathogen
-Antigenic variation, or altering the bacterial structures to which the antibodies bind
-Rapid turnover of pili structures to shed any bound antibody
How do pathogens penetrate the skin?
they rely on injuries like cuts or wounds
What mechanisms do pathogens use to penetrate the mucous membranes?
-directed uptake by cells
-exploiting antigen-sampling processes
Directed uptake by cells
pathogen attaches to cell and induces non-phagocytic cells to engulf them via endocytosis
type III secretion system
injectisome - drills holes in host cell and injects effector proteins which induces engulfment
ruffling
(result of rearranged actin molecules from the injectisome) ruffles on cell surface that enclose
bacteria and bring them into the cell
exploiting antigen-sampling processes
M cells pass pathogens through intestinal barrier to macrophages, some pathogens can survive
the macrophages and induce apoptosis then binds to epithelial cells to induce uptake
What are the 4 ways bacteria avoid host defenses?
-hiding within a host cell
-avoiding destruction by phagocytes
-avoiding killing by complement system proteins
-avoiding recognition by antibodies
hiding within a host cell
, pathogens enter host cells which allows them to avoid complement proteins, phagocytes, and
antibodies (all outside the cell)
avoiding destruction by phagocytes
some pathogens can avoid being recognized altogether or have mechanisms to survive being
engulfed by a phagocyte (C5a peptidase, membrane-damaging toxins, capsules, M-proteins, Fc
receptors)
avoiding killing by complement system proteins
microbe hijacks the host cell's mechanism to prevent their surfaces from activating the
complement system. microbe binds host cell's regulatory proteins to avoid activating the
membrane attack complex (MAC)
avoiding recognition by antibodies (bacteria)
-IgA protease: splits IgA antibodies (in mucosal surfaces)
-antigenic variation: alter surface antigens - stay ahead of antibody recognition
-mimicking host molecules: mimic a host molecule/structure to appear as self instead of foreign
(immune system does not attack "self" cells)
direct damage to the host
toxins
indirect damage to the host
immune response
exotoxins
proteins with specific damaging effects (gram-negative and gram-positive bacteria)
endotoxins
lipopolysaccharide components of the outer membrane of gram-negative bacteria (Lipid A is the
toxic component)
neurotoxins
exotoxins that damage the nervous system
enterotoxins
exotoxins that disturb the intestines
cytotoxins
exotoxins that damage a variety of cells
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