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Chronic granulomatous disease
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chronic granulomatous disease p. 107
catalase-positive microbes p. 183
immunodeficiencies and p. 115
recombinant cytokines for p. NaN
respiratory burst in p. 107
When a phagocyte detects a pathogen, it stretches itself out as if it had two little arms.
These arms wrap around the pathogen and seal themselves back up, forming a vesicle inside the phagocyte called a phagosome.
Because the phagosome is lined by what was previously part of the phagocyte's surface membrane, whatever structures were previously surface-bound, like this protein complex called NADPH oxidase, end up inside the phagosome.
The phagocyte also has other organelles, like lysosomes, which are full of digestive enzymes that can destroy a pathogen.
When a lysosome fuses with a phagosome, it forms a phagolysosome, and lysosomal enzymes start to destroy the pathogen.
The lysosomal enzymes also activate NADPH oxidase, which came from the phagosome, causing NADPH to undergo oxidation, and lose one of its electrons.
Nearby oxygen molecules can grab these electrons to become reduced and form superoxide ions, or O2- ions.
Another enzyme, superoxide dismutase, can take these ions and combine them with hydrogen ions to form hydrogen peroxide, or H2O2.
This process of producing superoxide ions and hydrogen peroxide is called the respiratory burst.
These ions and molecules destroy pathogens by damaging their cell membranes and proteins.
In chronic granulomatous disease, there’s a mutation in the genes that code for NADPH oxidase, so the enzyme is less functional.
Chronic granulomatous disease (CGD) is a genetic condition, in which neutrophils and macrophages cannot create superoxide radicals to kill engulfed germs. There is a mutation in NADPH oxidase genes. People with CGD have problems fighting infections because they don't have enough neutrophils to fight bacteria and other germs.
People with CGD often get recurrent and severe infections, especially in their lungs, ears, and sinuses. They may also develop skin abscesses or sores that don't heal properly. People with CGD struggle to fight off infections caused by catalase-positive bacteria, such as S. aureus, Serratia, Klebsiella, Aspergillus, and Burkholderia.
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