Neutrophils reach the lung in two waves following mycobacterial infection.

<p>Wild-type C57BL/6 mice were infected with 5x10⁶ CFU of BCG or 10³ CFU of Mtb and euthanized at the time points indicated. Cells were obtained from the lung tissue or airspace from individual animals. (<b>a</b>) Combined labeling with anti-CD11b, anti-Ly-6C and anti-Ly-6G antibodies was used to identify neutrophils among the cells present in the lung. The characteristic polylobed nucleus of neutrophils was observed in CD11b Ly-6C Ly-6G triple-positive cells from the R2 gate after flow cytometry sorting and May Grünwald Giemsa labeling. Slides were observed under an Eclipse 80 microscope (Nikon instrument) equipped with a 40 x objective. (<b>b, c</b>) We determined the numbers of neutrophils present in the lung tissue by flow cytometry for C57BL/6 mice killed on days 1, 3, 7, 23 and 56 post infection. Lung neutrophil numbers were determined after infection with BCG (<b>b</b>) or Mtb (<b>c</b>) Data from two independent experiments (n = 5–10). Kruskal-Wallis with Dunn’s <i>post hoc</i> test *<i>P</i><0.05, ** <i>P</i><0.01, *** <i>P</i>< 0.001.