In mice, giving thymosin‑alpha‑1 a few times raised the number of blood‑forming colonies by making the body produce more of a growth factor called IL‑3. The peptide didn’t work directly on bone‑marrow cells in a dish, so its effect seems to be indirect through IL‑3. This hints it could help boost immune cell production, but the study is early‑stage and done in special mice, so we don’t yet know how to use it in people.

We have studied the action mechanism of thymosin alpha 1 in modulation of haemopoietic system. The present study demonstrated that thymosin alpha 1 enhanced the colony formation as determined by CFU-s, GM-CFU and T-CFU, as well as the production of IL-3, when administered twice a week for a total of six or twelve times into nu/nu mice. The incubation of bone marrow cells with thymosin alpha 1 in vitro did not cause an increase of CFU-s, in contrast to IL-3 which caused a marked increase of CFU-s during the incubation of 72 h. These experiments indicate that thymosin alpha 1 exerts its effect on colony formation of haemopoietic stem cells (CFU-s) indirectly through the enhancement of the IL-3 production. The present finding may support clinical applications of thymosin alpha 1 in a wide range, since IL-3 is known to be the growth factor for many kinds of haemopoietic precursor cells including not only CFU-s but also GM-CFU, BFU-E, Eos-CFU, Meg-CFU, Mast cells, Pre B-cells and Pre T-cells.