Figure 2. Immunohistochemical staining for stem cell factor (SCF). Vascular endothelial cells and stromal cells expressed strong immunoreactivity for SCF in a membrane from a patient with active proliferative diabetic retinopathy (PDR). A: Low power, original magnification 40×. B: high-power, original magnification 100×. SCF immunoreactivity is absent in a membrane from a patient with inactive PDR. Note that the membrane is composed mostly of fibrous tissue (C: original magnification 40×). Immunohistochemical staining for granulocyte colony-stimulating factor (G-CSF). G-CSF immunoreactivity was observed in vascular endothelial cells (D: original magnification 100×). Immunohistochemical staining for endothelial nitric oxide synthase (eNOS). Immunoreactivity for eNOS was observed in vascular endothelial cells (E: original magnification 100×) and stromal cells (F: Low-power, original magnification 40× and G: high-power, original magnification 100×).