Localization of VIP receptors, SS receptors, and SP receptors in a human thymus. (A) Hematoxylin-eosin stained section. Bar = 1 mm. (B) Autoradiogram showing total binding of¹²⁵I-VIP. VIP receptors are diffusely distributed in cortex and medulla. (C) Autoradiogram showing total binding of¹²⁵I-Tyr³-octreotide. SS receptors are located in the medulla. (D) Autoradiogram showing total binding of¹²⁵I-BH-SP. SP receptors are located in blood vessels.