Allogeneic bone marrow transplantation in man: in vitro activity of FTS-Zn on T-cell markers and functions.

Thymulin (FTS-Zn) is a synthetic metallo-nonapeptide similar to the serum factor of thymic origin FTS, which induces the maturation of lymphoid cells. The activity of this compound on peripheral blood mononuclear cells from 12 bone marrow recipients was studied in vitro. It was demonstrated that thymulin was able to induce or modulate the expression of T-cell membrane markers, to enhance the proliferative responsiveness of lymphocytes to mitogens or allogeneic cells, and to increase mononuclear cells' natural killer activity. This in vitro responsiveness was contemporary to a transient decrease of FTS levels in the patients' serum, documented by sequential assays. These results suggest that thymulin could be of interest as a prophylactic therapy to speed up the immunological reconstitution of bone marrow recipients.