Page 857 - Veterinary Immunology, 10th Edition

exposure to HOCl and then binds and protects essential proteins
VetBooks.ir against bleach-induced aggregation.

Bacteria such as enteropathogenic E. coli, Yersinia pestis, M.
tuberculosis, and P. aeruginosa secrete molecules that can reduce

their death by neutrophils. For example, E. coli produces lysozyme
inhibitors. Other bacteria ensure that they are never exposed to
these enzymes by interfering with phagosomal maturation (Fig.
26.7). Mycobacteria, Aspergillus flavus, B. abortus, and Chlamydophila

psittaci can establish themselves within vacuoles that exclude
proteases and oxidants by blocking lysosome-phagosome fusion. In
the case of M. tuberculosis, the bacterium enters the macrophage
through cholesterol-enriched membrane microdomains that are

coated on the cytosolic side with a protein (tryptophan-aspartate-
containing coat protein, or TACO) that prevents phagosome
maturation. Thus lysosomes cannot fuse with the phagosome. They
remain distributed within the cytosol, and the bacteria continue to

survive and grow. Mycobacteria also prevent acidification of
phagosomes by preventing recruitment of the proton pump
adenosine triphosphatase from the vacuolar membrane so that
lysosomal cathepsins remain inactive. Another mechanism used by

bacteria to avoid destruction is simply to escape from the
phagosome by migrating into the cytosol surrounded by a coat of
polymerized actin. This method is employed by mycobacteria and
by L. monocytogenes. Listeria secretes listeriolysin O that destroys

cell membranes and so permits the organism to enter the cytosol
(Table 26.1).

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