Thymosin α1 and thymosin β4 are the first peptides with immunomodulatory activity isolated from thymosin fr. 5. The levels of both vary in different patients and can therefore reflect the health status of the body.

Thymosin α1 has a molecular weight of 3108 and is active in a variety of in vitro and in vivo tests of T cell differentiation and function. The biological properties of Thymosin α1 include the induction of T cell markers, stimulation of lymphokine production such as MIF and interferon, and reconstitution of immunosuppressed mice. Due to its immune repair properties, it is currently being tested as an adjunct to cancer therapy.

Thymosin β4, with a molecular weight of 4,982, does not have the same immunological properties as Thymosin α1, although its biological profile is less clear. It is active in inducing terminal deoxynucleotidyl transferase (TdT) in myeloid cells in vitro and in inducing TdT in immunosuppressed mice. It also induces the release of luteinising hormone-releasing hormone (LHRH) and luteinising hormone (LH) in the hypothalamic-pituitary compartment in vitro, and in vivo when injected into the mouse brain. Serum thymosin β4 levels were significantly suppressed in functionally castrated and postmenopausal women, providing further evidence for the association of thymosin β4 with the pituitary-reproductive axis .

The study showed that in the same serum samples, Thymosin α1 levels were 670 ± 163 pg/ml in normal males and 652 ± 162 pg/ml in females.thymosin β4 levels were 974 ± 400 ng/ml in normal men and 889 ± 345 ng/ml in women. In addition, Thymosin α1 and thymosin β4 levels were elevated in patients with AIDS (57% and 48%, respectively), but Thymosin α1 levels were more markedly elevated in patients with AIDS-related immune dysfunction (54% vs 15%). Thymosin α1 levels were also higher in thymomas than in normal thymus (273.9 ± 205.0 ng/mg protein vs 45.0 ± 52.1 ng/mg protein). Thymosin α1-like immunoreactivity levels were relatively higher in the thymus of patients with myasthenia gravis than in patients with normal thymus.

Elevated serum levels of Thymosin α1 have been reported in pregnant women and their newborns, with maternal levels (1,207 ± 947 pg/ml) tending to be higher than those in healthy adults (1,043 ± 576 pg/ml). Mixed cord serum levels (1,466 ± 940 pg/ml) were higher than maternal levels. This suggests that maternal Thymosin α1 levels may reflect foetal levels.

References:

[1] PAUL H. NAYLOR . Thymosin α1 and thymosin β4 in serum: Comparison of normal, cord, homosexual and AIDS serum[J]. International journal of immunopharmacology, 1986. DOI:10.1016/0192-0561(86)90001-9.

[2] ROBERT A. WELCH. Maternal and Fetal Circulating Levels of Thymosin α1 During Parturition[J]. ACS Applied Bio Materials, 1987. DOI:10.1111/j.1600-0897.1987.tb00108.x.

[3] HIROAKI NARUSE MD. Immunoreactive thymosin α1 in human thymus and thymoma[J]. ACS Applied Energy Materials, 1993. DOI:10.1016/S0022-5223(19)33979-0.