Immunohistochemical analysis of CD11b in formalin-fixed sections of popliteal LNs of naïve and <i>B</i>. <i>anthracis</i>-challenged mice.

<p>(A) In naïve mice the CD11b+ cells with monocyte/macrophage morphology were localized to subcapsular and medullar regions. (B) In the Sterne strain-infected mice at day 2 post infection the amount of CD11b antigen (stained brown) was increased and associated mainly with the areas of bacterial growth (circled in the middle panel). The LNs demonstrated a widespread cell death and tissue necrosis. Numerous bacterial chains are visible as gray shadows (arrows, right panel). (C) The LN tissue of the dSterne-infected mice demonstrated no gross pathology and the isolated CD11b+ cells scattered through LN parenchyma (arrows).