Fig 2: Grading scale for immunohistochemical staining of soluble fms-like tyrosine kinase 1 (sFLT1) in kidney biopsies: sFLT1-positive cells that constituted more than 50% of the inflammatory infiltrate (grade 4), 25%–50% (grade 3), 10%–25% (grade 2), 10% (grade 1), and <10% (grade 0.5). Bars = 20 µm.

Fig 3: Representative images of immunohistochemical assay for soluble fms-like tyrosine kinase 1 (sFLT1), CD68 (macrophage marker), and CD34 (endothelial marker) immunoreactivity (brown precipitate) in renal biopsies. Bars = 20 µm. G, glomerulus.

Fig 4: Upper panels (interstitial nephritis case): representative images of immunofluorescence assay for soluble fms-like tyrosine kinase 1 (sFLT1; red) and CD34 (endothelial marker; green) in a renal biopsy. The areas to the right of the asterisks show reduced or absent CD34 staining. Bars = 100 µm. Lower panels (anti-neutrophilic cytoplasmic antibody case): representative images of immunofluorescence assay for sFLT1 (red), and CD68 (macrophage marker; green) in a renal biopsy. Yellow immunofluorescence demonstrates colocalization of the 2 antigens, which demonstrates that macrophages express sFLT1 in kidney interstitium. Bars = 20 µm.

Fig 5: The expression of soluble fms-like tyrosine kinase 1 (sFLT1) in kidney biopsies is positively correlated with kidney inflammation (n = 52 biopsies). sFLT1 protein expression localized in kidney biopsies by immunohistochemistry. A 4-tier grading system was used to semiquantitatively measure sFLT1 and inflammation in the kidney biopsies.