Our gene expression analysis implicated significant presence of M2 macrophages in influenza infected mammary glands by the upregulation of the M2 specific transcripts CD163, CLEC7A, M5R1, CD209, LGMN, and MRC1. M2 macrophages have a similar phenotype as tumor associated macrophages (TAM), since they regulate MMPs and support a microenvironment favorable for oncogenesis [47]. This evidence concerns the gene MRC1 and influenza.