Alternatively activated macrophages derived from monocytes and tissue macrophages are phenotypically and functionally distinct

Macrophages adopt an alternatively activated phenotype (AAM) when activated by IL-4. While these AAMs can be derived from local proliferation of resident tissue macrophages or recruited inflammatory monocytes, it is not known whether these different AAMs are phenotypically and functionally distinct. Using microarray analysis of gene expression, we demonstrated that while both monocyte- and tissue-derived AAM expressed high levels of Arg1, Chi3l3 and Retnla, only monocyte-derived AAM upregulated Raldh2 and PD-L2. The distinction between monocyte- and tissue-derived macrophages can, therefore, be made using different phenotypic markers. Gene expression profiling analysis with whole genome microarray of tissue-derived and monocyte-derived macrophages, induced using IL-4c and/or 4% thioglycollate.