ARG1 and infection: We, therefore, conducted double staining of mycobacteria and NOS2 or Arg1 in lung sections of LysMcreSOCS3loxP/loxP mice 1 week after infection with Mtb. In SOCS3loxP/loxP mice, NOS2- and Arg1-expressing cells were not detectable at this early time point (data not shown) reflecting the low gene expression of both enzymes (see Figures 3A,B).