MRC1 and silicosis: Furthermore, while it is still unknown whether resident AMs are plastic and change their phenotype during the early stages of silicosis or if they are derived from circulating monocytes (36), the current data show that the number of non-inflammatory M2-like CD206+MHCII- AMs from Axl-SIL was dramatically reduced whereas the number of M1-like MHCII+CD206- AMs was elevated, which likely contributes to chronic inflammation.