Retina and spleen samples were homogenized in RIPA buffer with a protease inhibitor (Roche, Basel, Switzerland). For sample preparation, 50 mg of protein were resuspended in 2x Laemmli loading buffer (pH 6.7) (Sigma-Aldrich) and heated at 95°C for 5 minutes. Electrophoresis was performed by loading 12 µL of sample in a 12% pre-cast SDS-PAGE gel (Bio-Rad Laboratories, Hercules, CA, USA), which was later transferred to a polyvinylidene difluoride (PVDF) membrane (Merck Millipore, Billerica, MA, USA). After 1 hour blocking with either 5% non-fat dried milk or 2% bovine serum albumin (Sigma-Aldrich) in Tris buffered saline, 0.05% Tween 20, membranes were incubated overnight at 4°C with the following primary antibodies: rabbit anti-mouse L-ferritin (1:1000; ab69090, Abcam, Cambridge, UK); rabbit anti-mouse H-ferritin (1:1000; ab65080, Abcam); rabbit anti-mouse SCARA5 (1:1000; ab76720, Abcam); rabbit anti-mouse transferrin (1:2000; PA3-913, Thermo Fisher Scientific, Wilmington, DE, USA); rat anti-mouse transferrin receptor (1:1000; ab63333, Abcam); rabbit anti-mouse claudin-5 (1:1000; 34-1600, Thermo Fisher Scientific); and rabbit anti-mouse VEGF (1:100; ab46154, Abcam). For protein normalization, rabbit anti-mouse α-tubulin (1:80000; ab4074, Abcam) or rabbit anti-human α smooth muscle actin (1:10000; ab5694, Abcam) were used as a loading control. Secondary antibodies goat anti-rabbit (Bionova Scientific, Fremont, CA, USA) and sheep anti-rat (LifeSpan, Providence, RI, USA) horseradish peroxidase at 1:5000, were used. Immobilon Crescendo Western HRP Substrate (Merck Millipore) and the ImageJ software were used for band detection and quantification, respectively.