Pathogenesis
In humans, L. pneumophila invades and replicates in macrophages. The internalization of the bacteria can be enhanced by the presence of antibody and complement, but is not absolutely required. A pseudopod coils around the bacterium in this unique form of phagocytosis. Once internalized, the bacteria surround themselves in a membrane-bound vacuole that does not fuse with lysosomes that would otherwise degrade the bacteria. In this protected compartment, the bacteria multiply.
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