Macrophages in the Adult Murine Heart Figure 2. Immunophenotype of cTMs within adult Cx3cr1GFP/+ mouse hearts. Representative histograms for myeloid (F4/80, CD11c, MHC-II (IAb), CD14, CD86) and lymphoid (CD3e, B220) related markers detected in CD45+CD11b+GFP+ population and CD45+CD11b2GFP2 population. Red line shows isotype control staining. Histograms representative of at least 4 experiments, with mouse group sizes of at least 4 mice. doi:10.1371/journal.pone.0036814.g002 cTMs have an M2 macrophage gene expression signature Microarray gene expression analysis of highly enriched genes in cTMs (Mrc1 and CD163) compared to GFP+ cells from the spleen and brain, indicated that these cardiac cells have a distinct gene expression signature resembling alternatively-activated, anti-in- flammatory M2 macrophages [11]. To determine if cTMs resemble M2-polarised macrophages, we analysed expression levels of 24 genes reportedly expressed in M2 macrophages in vitro and in vivo [12,20]. Indeed, 21 of 24 M2 genes (represented by 34 probe sets) were highly expressed in cTMs (Fig. 4 a and PLoS ONE | www.plosone.org 5 May 2012 | Volume 7 | Issue 5 | e36814