Research Article

Local Macrophage Proliferation, Rather than Recruitment from the Blood, Is a Signature of TH2 Inflammation

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Science  12 May 2011:
DOI: 10.1126/science.1204351


A defining feature of inflammation is the accumulation of innate immune cells in the tissue that are thought to be recruited from the blood. We reveal that a distinct process exists in which tissue macrophages undergo rapid in situ proliferation in order to increase population density. This inflammatory mechanism occurred during T helper 2 (TH2)–related pathologies under the control of the archetypal TH2 cytokine interleukin-4 (IL-4) and was a fundamental component of TH2 inflammation because exogenous IL-4 was sufficient to drive accumulation of tissue macrophages through self-renewal. Thus, expansion of innate cells necessary for pathogen control or wound repair can occur without recruitment of potentially tissue-destructive inflammatory cells.