Expression of EGFP in adult tissues examined by fluorescence microscopy.

Adult tissues were fixed on 4% paraformaldehyde, incubated overnight in 18% sucrose, embedded in optimal cutting temperature (OCT) media and frozen sectioned. (A) Left, splenic macrophages expressing EGFP. These cells are located mainly in the red pulp of the spleen. RP indicates red pulp; WP, white pulp. Right, FACS analysis of enzymatically digested spleen revealed about 18% of cells expressing EGFP. (B) In the liver, EGFP is expressed in the Kuppfer cells (left). These EGFP⁺ cells constituted about 8% of the cell population, as shown in the FACS profile of the liver (right). (C) Expression of EGFP in the alveolar and interstitial lung macrophages, which composed about 8% of the whole cell population. (D) Abundant EGFP⁺ cells were observed in the lamina propria of the small intestine and constituted about 7% of the whole cell population. EGFP⁺ cell gates (M2) in the FACS profiles were made based on the nontransgenic littermate control profiles. (E) Brain macrophages (microglia) expressed EGFP. (F) Examination of the cross section of the eye revealed the expression of EGFP in microglia (arrow) in the retina. Renal interstitial macrophages (G) are EGFP-positive, as are macrophages that reside in the interstitium of testis (H). (I) Bone-resorptive osteoclasts expressed EGFP. (J) A cross-section of the ear revealed the expression of EGFP in Langerhans cells (arrow) and epidermal macrophages. (K) EGFP expression in Langerhans cells in the epidermal sheet of the ear. (L) Thymic macrophages shown to express EGFP.