A Strategic Defense

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Science  05 Oct 2012:
Vol. 338, Issue 6103, pp. 19
DOI: 10.1126/science.338.6103.19-c

Just as in American football, during the immune response, the location of your defenders is key. One player out of line can make the difference between a sack or a touchdown, or in the case of the immune system, a localized versus systemic infection. How the immune system orchestrates this careful defense, however, is not well understood. Kastenmüller et al. now demonstrate that the organization of cells within the lymph nodes of mice is critical for preventing pathogen spread during the first few hours of an infection. Infecting bacteria drain to nearby lymph nodes, where they are immediately collected by a specially localized population of macrophages. Although these macrophages have antimicrobial activity, the immune system takes further precautions to ensure that the infection does not spread. Several types of lymphoid cells are localized near these macrophages. In response to bacteria, an inflammasome-dependent mechanism drove macrophages to produce the cytokine interleukin-18, which in turn alerted the nearby lymphoid cells to the threat. In response, the lymphoid cells produced the cytokine interferon-γ, which enhanced the antimicrobial activity of the macrophages, thus keeping the infection in check.

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