Biologic activities of various thymus preparations.

Thymosin and THF were prepared from total normal calf thymus (TT), from calf thymus depleted of thymocytes by whole-body irradiation (TE), and from calf thymus lymphocytes (TL). The activities of these products were compared in four different in vitro assays that monitored for various T-cell functions. The results suggest that the preparations obtained from thymus epithelium are more active in inducing T helper cell function in nude/nude mouse spleen cells than substances isolated from thymus lymphocytes. The latter seem to act on a more advanced step in the T cell line differentiation.