Fig. 2

TH + innervation of normal human spleens using VIP chromogen and citrate buffer antigen retrieval. Sympathetic nerves were located primarily in the adventitia surrounding blood vessels and only rarely extended into the white pulp (wp). A A longitudinal cut showing the splenic artery (sa) and sympathetic innervation within the surrounding adventitia. Arrow indicates a nerve bundle. B Sympathetic innervation of a moderate-sized central arteriole (ca.) within white pulp. C Higher magnification image of a smaller arteriole surrounded by nerves. D Sympathetic nerves run along a blood vessel cut longitudinally. Arrows indicate TH + nerves extending a short distance into the surrounding white pulp. E Higher magnification of same arteriole in panel D showing nerves (arrows) protruding into the white pulp. F Arrows indicate TH + nerves cut in cross-section within the capsule (c). Note the absence of innervation in the red pulp (rp) to the right