Verification of SPIO-labeled granulocytes isolated from infected tissue.

<p>(A) Fraction of granulocytes isolated from infected tissue of rats treated with SPIO-labeled granulocytes. SPIO-labeled granulocytes (blue) were identified by Prussian blue staining. (B) fraction of granulocytes isolated from infected tissue of rats from the control group, which were treated with unlabeled granulocytes. Re-isolated granulocytes are completely negative for Prussian blue staining. The scale bar equals 20 µm.</p

Histological sections of the infected tissue.

<p>(A–C) Prussian blue staining of infected tissue samples from rats that received SPIO-labeled granulocytes. SPIO-labeled granulocytes (blue) accumulated within the infected tissue together with unlabeled granulocytes. The scale bar equals in (A) 250 µm, (B) 100 µm, (C) 25 µm. (D–F) Prussian blue staining of infected tissue samples from control rats. Massive infiltration of unlabeled granulocytes into the whole infected region. The scale bar equals in (D) 250 µm, (E) 100 µm, (F) 25 µm.</p

Detection of experimentally induced subcutaneous inflammatory process.

<p>T2*-weighted MRI axial images of the left pectoral area of infected rats. (A–C) Inflammatory area in the left pectoral region (ellipse) directly after inoculation of the staphylococcal suspension and (A) before injection of SPIO-labeled granulocytes, (B) 6 h after injection of the SPIO-labeled granulocytes including several spots with significant loss of signal intensity inside the inflamed area (white arrows). (C) Inflammatory area in the left pectoral region 12 hours after injection of SPIO-labeled granulocytes including multiple single spots (white arrows) with significant loss of signal intensity inside the inflamed area. (D–F) Inflammatory area in the left pectoral region (ellipse) of a control animal directly after inoculation of the staphylococcal suspension and (D) before injection of non-labeled granulocytes, (E) 6 h and (F) 12 h after injection of the non-labeled granulocytes. Areas of signal intensity loss could not be detected at any time in the control animals.</p

Histological verification of SPIO labeled granulocytes distribution.

<p>(A) Granulocytes were transfected <i>in vitro</i> with SPIO particles. Transfection efficiencies reached up to 90% as estimated by Prussian blue staining. Iron particle presence is identified as blue dots within cells. The scale bar equals 20 µm. (B) Unlabeled control granulocytes. Cells were counterstained with Nuclear Fast Red. The scale bar equals 20 µm.</p

Comparision of Relative Signal Intensity over time.

<p>The relative SI was calculated by dividing SI of infected area by SI of noninfected area on T2*-weighted GRE images before (t = 0 h), after 6 and 12 h following the application of granulocytes (median values). Squares: experimental group receiving SPIO-labeled granulocytes. Circles: control group receiving unlabeled granulocytes. The difference of relativ SI over time was most prominent 12 h after SPIO application.</p

Granulocyte enrichment from rat whole blood.

<p>Granulocytes were stained using FITC-labeled HIS48 antibody and were examined by flow cytometry. (A) Granulocytes constituted 3% of the whole blood fraction before enrichment. (B) Granulocyte fraction increased to 57% after dextran sedimentation of erythrocytes. (C) Purity of granulocytes was 98% after density gradient centrifugation and removal of residual erythrocytes with the red blood cell lysis solution.</p

Comparison of MRI axial images of the inflammatory area.

<p>Different MRI image types 12 hours after bacterial inoculation (ellipse). (A–C) Representative images of a rat which received SPIO-labeled granulocytes. (D–F) Representative images of a rat from the control group which received unlabeled granulocytes. (A, D) T2* weighted images; (B, E) computed susceptibility weighted images (SWI); (C, F) T2-mapping computed images. Maximal loss of signal intensity was detected in T2* weighted images (D).</p