Thymocyte development is dosage dependent on Shh protein. immunohistochemical analysis of samples after injecting varying concentrations of Shh are displayed. In all experiments optimal dosage of Shh appears to be 0.0005 micrograms per milliliter, thymocyte proliferation (A, C) is optimal at this concentration and decreases in either direction of concentration manipulation. Proliferation of Tcells to the double positive (DP) stage is also displayed in images (B, E, and F). This optimal concentration is maintained in study of CD4 and CD8 proliferation.