Fig. (2).

Labeling of mouse platelets with the red dye PKH26 and infusion into mice. Freshly isolated mouse platelets were stained with PKH26 and characterized by FACS (A) or by fluorescence microscopy (B& C). The fluorochrome PKH26 is seen in the red channel (EX 535/50, EM 610/75) and is not seen in the green channel (EX 480/40 nm, EM 527/30 nm) (C). Freshly isolated red platelets (5x10⁸ in 100 µl) were injected via the tail vein and analyzed in the liver (D&E), lung (F&G) or brain (H&I) after 24 hr. The platelets were either stained by CD61⁺ immunohistochemistry using DAB chromogen (D, F, H) or directly by their fluorescence (E, G, I). In the liver strong CD61+ platelets were seen in hepatic vessels (* in D), but not in the liver tissue (Lt). In the lung CD61⁺ platelets were seen in the lung vessels (* in F) and in alveoli tissue (Al) but not in bronchioles (Br). In the brain, platelets were found in the plexus choroideus (* in H). Red platelets were poorly seen in the brain and associated with vessels (I). Scale bar = 6 µm (B&C) and 50 µm (D-I). (The color version of the figure is available in the electronic copy of the article).