Thymulin

Thymulin, originally named facteur thymique sérique (FTS), is a nonapeptide hormone produced by thymic epithelial cells (peptide component C33H54N12O15, 858.9 g/mol). Its biological activity and antigenicity depend on zinc bound within the molecule. Monoclonal antibody studies identified epitopes recognized only on the zinc-coupled form, indicating a zinc-specific conformation, consistent with NMR data showing a distinct structure for the zinc-containing hormone. Thymulin was discovered in the early 1970s and characterized as a thymic hormone involved in aspects of intrathymic and extrathymic T-cell differentiation.

Thymulin in the research literature

Early work characterized thymulin as a factor that induces T-cell differentiation and modulates functions of several T-cell subsets, with its effects on suppressor T cells considered the most pronounced. Studies with thymic explants from old mice reported that thymulin output in short-term culture was similar to that of young thymuses but that the zinc-bound form was nearly absent, and that adding zinc to the cultures restored it.

Later research has examined links between thymulin and the neuroendocrine system, including evidence that its secretion is influenced by neuroendocrine signals and that it acts as a hypophysotropic peptide. In fetal alveolar type II epithelial cell culture, thymulin reduced endotoxin-induced IL-1β release, increased cAMP, and reduced nuclear translocation of the NF-κB subunit RelA (p65).