1. ¹Department of Immunology, Genentech Inc., South San Francisco, CA, USA
2. ²Department of Bioinformatics, Genentech Inc., South San Francisco, CA, USA

Correspondence: Dr HF Clark, Departments of Bioinformatics and Immunology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA. E-mail: hclark@gene.com

³These authors contributed equally to this work.

Received 3 July 2007; Revised 8 October 2007; Accepted 9 October 2007; Published online 13 November 2007.

Abstract

Tissue-resident macrophages play an important role in defense against pathogens and perform key functions in organ homeostasis, innate and adaptive immunity. Tissue macrophages originate from blood monocytes that infiltrate virtually every organ in the body. Macrophages in different tissues share many characteristics, including their ability to migrate, phagocytose particles, metabolize lipids and present antigens. Morphologically they are quite heterogeneous, and some distinct functions have been reported. The gene expression profile of macrophages is reflective of both their shared and distinct biological functions. Here, we show that macrophages from murine spleen, liver and peritoneum display dramatically different expression profiles. Clusters of genes were found to represent unique biological functions related to adhesion, antigen presentation, phagocytosis, lipid metabolism and signal transduction. Some gene families, such as integrins, are differentially expressed among the macrophages resident in different tissues, suggesting that the tissue of residence influences their biological function.