Research Report On Infection Of The Lung ( Fig ) Essay

1027 Words Jul 2nd, 2015 5 Pages
to Mtb infection in the lung (Fig. 1). In strong support of this concept, studies in zebrafish have demonstrated the ability of Mtb to manipulate the earliest recruitment of macrophages. This activity has been linked to the capacity of the bacterium to express lipids on its cell surface. Specifically, expression of the Mtb molecule phthiocerol dimycoceroserate (PDIM) limits innate recognition of Mtb, thereby reducing recruitment of Toll-like receptor (TLR)–activated macrophages28. In addition to this subversion of the pathogen-recognition pathway, other lipids on the Mtb surface—the phenolic glycolipids (PGLs)—drive recruitment of permissive macrophages via a pathway that depends on the chemokine CCL2 and the chemokine receptor CCR2 (ref. 28). One other defense pathway may be neutrophil recruitment. Specifically, studies in contacts of people with pulmonary TB found that the risk of infection (not disease) was inversely associated with the number of neutrophils in the blood of the individuals tested and that the neutrophils were themselves antibacterial29 (Fig. 1). Although this study did not directly define the role of neutrophils in early control of infection, it suggests a working model for an underlying mechanism whereby some people do not show signs of infection despite heavy exposure.
The above observations support the hypothesis that the outcome of Mtb infection in the lung depends on the initial environment encountered by the bacterium. This environment depends on…

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