Gr1<sup>int</sup> CD11b<sup>+</sup> FSC<sup>low</sup> cells predominate in the lungs of NOS2-/- mice.

<p>Further analysis of CD11b<sup>+</sup>FSC<sup>low</sup> and CD11b<sup>+</sup>FSC<sup>high</sup> cells was performed by staining with anti-Gr1 antibody. As determined by mean fluorescence intensity, CD11b<sup>+</sup>FSC<sup>high</sup> had significantly higher Gr1 expression than CD11b<sup>+</sup>FSC<sup>low</sup> (A). Starting at early time points NOS2-/- mice but not WT C57BL/6 mice have a significant number of cells giving an intermediate staining pattern for Gr-1 (B). At later time points, the influx of CD11b<sup>+</sup>FSC<sup>high</sup> cells into the lungs of NOS2 -/- mice is also enhanced (C). Results are expressed as the Log mean cell number (± SEM, n=5) in the lung. Gr1<sup>high</sup> CD11b<sup>+</sup> FSC<sup>high</sup> cells express markers compatible with a monocytic lineage. Both populations of Gr1 expressing cells were further analyzed by flow cytometry using the monocytic markers Ly6C, CD14 and F4/80 (D). As determined by the mean fluorescence intensity for these markers, a more precise phenotype for these two cellular populations would be Gr1<sup>high</sup> CD11b<sup>+</sup> FSC<sup>high</sup> Ly6C<sup>high</sup> CD14<sup>+</sup> F4/80<sup>+</sup> and Gr1<sup>int</sup> CD11b<sup>+</sup> FSC<sup>low</sup> Ly6C<sup>low</sup> CD14<sup>low</sup> F4/80<sup>low</sup>, compatible with a monocytic and granulocytic lineage, respectively. Results are expressed as the log mean cell number (± SEM, n=5) in the Lung. ***Student t test, * p<0.05, ** p<0.01, *** p<0.001.</p>