Thymosin alpha-1 (Tα1) is a 28-amino-acid peptide, acetylated at its N-terminus, first purified from calf thymus tissue in the 1970s. It is one of the most heavily published peptides in immunology research, studied mainly for how it engages Toll-like receptors on dendritic cells and shapes the T-cell responses that follow.
Under the name thymalfasin it has been approved as a medicine in a number of countries outside the United States. It is not approved by the FDA, and the material described here is supplied for laboratory research only.
At a glance
| Also known as | Tα1, thymalfasin |
| Sequence | Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN-OH |
| Length | 28 residues, N-terminally acetylated |
| Molecular weight | ≈3,108 Da |
| Origin | N-terminal fragment of prothymosin alpha; first isolated from thymosin fraction 5 (calf thymus) |
| Targets studied | Toll-like receptors, principally TLR2 and TLR9, on dendritic cells and monocytes |
| US status | Not FDA-approved; research use only |
Where it came from
In the 1960s and 70s Allan Goldstein’s group fractionated calf thymus into a crude extract called thymosin fraction 5, which contained dozens of peptides. In 1977 they purified and sequenced one of its components, thymosin alpha-1, the first thymic peptide of its kind to be fully characterized.
Later work showed that Tα1 is not a thymus-specific hormone in the classical sense. Its sequence matches the first 28 residues of prothymosin alpha, a larger protein expressed in many tissues. Solid-phase synthesis then made a single, defined sequence available, replacing the variable extracts used in early studies.
Structure
Tα1 is a highly acidic peptide: glutamate and aspartate residues give it a strong net negative charge at neutral pH. In water it is largely unstructured. Spectroscopic and NMR studies in membrane-mimicking solvents have described partial helical structure, which has been proposed as relevant to how it interacts with cell membranes.
The N-terminal acetyl group is part of the native sequence and is reproduced in synthetic material. When reviewing a certificate of analysis for this peptide, the expected mass should account for it.
What the research has looked at
Dendritic cells and Toll-like receptors. The most cited mechanistic work comes from Luigina Romani’s group. In 2004 they reported that Tα1 activated dendritic cells through MyD88-dependent Toll-like receptor signaling, increasing IL-12 production and Th1-type responses in a murine model of fungal (Aspergillus) infection.
Tolerance as well as activation. A follow-up study in 2006 found that Tα1 also induced the tryptophan-degrading enzyme IDO in dendritic cells through TLR9, with IL-10 production and the generation of regulatory T cells. Together the two papers frame Tα1 as a modulator that balances inflammation and tolerance rather than a simple immune stimulant.
Earlier immunology. Older literature examined effects on thymocyte differentiation, T-cell maturation markers, IL-2 production and natural killer cell activity, mostly in rodent models and human peripheral blood cell cultures.
Typical models. Human peripheral blood mononuclear cells and monocyte-derived dendritic cells in culture, murine infection and immunization models, and a body of clinical-stage work conducted outside the US.
Research status and limits of the evidence
Thymalfasin was developed commercially in the 1990s and has been approved in a number of countries, mainly for chronic hepatitis B. Much of the clinical literature consists of small or open-label studies, and results across indications are mixed.
In the United States Tα1 is not an approved drug, and its status in the compounding framework has shifted more than once in recent years. Any material sold as a research reagent, including ours, is not for human or veterinary use.
Handling in the lab
Thymosin alpha-1 is supplied as a lyophilized powder. Lyophilized peptides are normally kept frozen, dry and away from light, and once reconstituted are kept refrigerated and used within a short window. See our reconstitution protocol for technique, and bacteriostatic vs sterile water for diluent choice.
Frequently asked questions
What is thymosin alpha-1?
A 28-residue, N-terminally acetylated peptide originally isolated from calf thymus and studied for its effects on dendritic cells, T cells and Toll-like receptor signaling.
Is thymosin alpha-1 the same as thymalfasin?
Yes. Thymalfasin is the international nonproprietary name for synthetic thymosin alpha-1 developed as a drug outside the US.
Is thymosin alpha-1 the same as thymosin beta-4 or TB-500?
No. Both names trace back to the same early thymus extract, but thymosin beta-4 is an unrelated 43-residue actin-binding peptide. TB-500 is a research peptide based on thymosin beta-4. See TB500.
Is thymosin alpha-1 FDA approved?
No. It is approved as a medicine in some other countries but not by the FDA. Isla Longevity supplies it for laboratory research only.
Purity and certificates
Every batch ships with a third-party certificate of analysis, published by batch number in our COA Bank. View Thymosin alpha-1 and its current COA. New to reading certificates? Start with how to read a certificate of analysis.
Related reading: What is KPV? · What is BPC-157? · How to read a COA
References
- Goldstein AL, Low TL, McAdoo M, et al. Thymosin α1: isolation and sequence analysis of an immunologically active thymic polypeptide. Proc Natl Acad Sci USA. 1977;74(2):725–729.
- Romani L, Bistoni F, Gaziano R, et al. Thymosin α1 activates dendritic cells for antifungal Th1 resistance through Toll-like receptor signaling. Blood. 2004;103(11):4232–4239.
- Romani L, Bistoni F, Perruccio K, et al. Thymosin α1 activates dendritic cell tryptophan catabolism and establishes a regulatory environment for balance of inflammation and tolerance. Blood. 2006;108(7):2265–2274.
Research use only
Isla Longevity supplies this compound for laboratory research use only. It is not approved by the FDA for human or veterinary use and is not for human consumption. This article summarises published research and is not medical guidance.
