Thymulin

Thymulin, also known as Facteur Thymique Sérique (FTS) or Serum Thymic Factor, is a nonapeptide (nine amino acids) hormone exclusively produced by thymic epithelial cells. Discovered in 1977 by Jean-François Bach and colleagues, thymulin is unique among thymic hormones in that it requires zinc as an essential cofactor for its biological activity. The zinc-thymulin complex is the only biologically active form of the peptide, making it a metallopeptide hormone.

Thymulin plays a fundamental role in T-cell differentiation and maturation. It promotes the differentiation of immature T-cell precursors into mature, functional T lymphocytes and modulates the activity of mature T cells. The peptide acts by binding to specific high-affinity receptors on T cells, influencing their proliferation, cytokine production, and cytotoxic activity. Thymulin also exhibits anti-inflammatory properties, partly through modulation of pro-inflammatory cytokine release.

Thymulin levels decline significantly with age as the thymus gland involutes, a process known as thymic involution. This decline is associated with the age-related deterioration of immune function, or immunosenescence. Research has explored whether restoring thymulin levels could partially reverse age-associated immune decline. Studies in aged animal models have shown that thymulin supplementation can restore certain T-cell functions and improve immune responses.

Beyond immunity, research has revealed thymulin's involvement in neuroendocrine regulation. Thymulin interacts with the hypothalamic-pituitary-adrenal axis and has been shown to modulate pain perception, pituitary hormone release, and inflammatory responses in the central nervous system. This neuroimmune crosstalk has made thymulin a subject of interest in neuroinflammatory conditions.