To determine whether the lung environment underlies one of the mechanisms accounting for the differences in the BM and lung Mks we wanted to see if BM Mks transferred into the lung would have an altered phenotype. BM Mks were isolated from naive WT mice and were stained with CellTrace Violet (Thermo Fischer Scientific, C34557) using the instructions from the manufacturer. Three million cells were transferred to naive WT mice via the o.p. route with either PBS or GFP E. coli. The mice were sacrificed 2 days later for flow cytometry.