FVIII localizes in the marginal sinus of the spleen with MZ B cells. FVIII-deficient mice were injected with saline (A), 4 μg of FVIII (B-C), or 25 μg of FVIII (D-E), followed by splenic harvest 15 minutes post injection. Frozen spleen sections were stained with polyclonal sheep anti-FVIII-FITC (yellow), B220-PE-CF594 (blue), and CD1d-PE (red). Images were obtained using the Leica SP8 multiphoton confocal microscope and are shown at 10× and 40× magnification. White box indicates area magnified at 40×. Arrows indicate colocalization of FVIII and CD1d (MZ B cells).