Thymosin‑alpha‑1 is a small protein that can boost the activity of immune cells like macrophages, helping the body spot and kill germs, and it may help recover immune function after chemotherapy that weakens the bone marrow. The research is still early and mostly done in labs and animal models, so it isn’t a finished guide for everyday use yet.

The innate immune response and its cellular effectors-peripheral blood mononuclear cells and differentiated macrophages-play a crucial role in detection and elimination of pathogenic microorganisms. Chemotherapy and some immunosuppressive drugs used after organ transplantation and for treatment of autoimmune diseases have, as main side effect, bone marrow suppression, which can lead to a reduced response of the innate immune system. Hence, many immune-depressed patients have a higher risk of developing bacterial and invasive fungal infections compared with immune-competent individuals. Thymosin α1 (Tα1) immunomodulatory activity on effector cells of the innate immunity has been extensively described, even if its mechanism of action is not completely understood. Here, we report some of the main knowledge on this topic, focusing on our in vitro and in vivo work in progress that reinforce the validity of Tα1 as a stimulatory agent for detection and elimination of pathogens by differentiated macrophages and for restoring immune parameters after chemotherapy-induced myelosuppression.