Codominant Expression

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These cells wall off the organism inside a granuloma called a tubercle. The localized concentrations of lysosomal enzymes in these granulomas can cause extensive tissue necrosis.

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Diphtheria

Natural infection with C. diphtheriae occurs only in humans and is spread by respiratory droplets. 

The organism colonizes the nasopharyngeal tract and causes little tissue damage, with only a mild inflammatory reaction. 

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Virulence is due to its potent exotoxin, which destroys the underlying tissue and results in heart, liver, and kidney damage, as well as to suffocation following formation of a tough fibrous membrane in the respiratory tract

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Malaria (Parasitic)

Sporozoites enter the bloodstream by mosquito.

The sporozoites migrate to the liver, where they multiply, transforming liver hepatocytes into giant multinucleate schizonts, which release thousands of merozoites into the bloodstream. 

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The merozoites infect red blood cells, which eventually rupture, releasing more merozoites. 

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Eventually some of the merozoites differentiate into male and female gametocytes, which are ingested by a mosquito and differentiate into gametes in the mosquito’s gut.