TH and Parkinson disease: At the end of the experiment (6 months after engraftment), the four PD monkeysincluding three controls were analyzed by brain slice staining.Immunohistochemical staining with DAB as a substrate revealed that TH-positivesignals were almost absent in the striatum of the lesioned side (Figures 3b and c), except at thetransplantation sites (Figures 3bʹ andbʹʹ), where intensive TH signals weredetected.