Thymalin (a natural thymic peptide mix) and Thymogen (a synthetic dipeptide) both boost immune cell activity, like T‑cell maturation and cytokine release, and Thymogen also enhances neutrophil movement and eating of pathogens. They were tested in people with chronic illnesses and immune problems, showing they can help regulate inflammation, though natural and synthetic versions act slightly differently.

Natural thymic peptides have been isolated from calf thymus by mild acid extraction. Pharmaceutical containing natural peptides (Thymalin) was put into practice as immunocorrector. One of the immunomodulatory molecules (L-Glu-L-Trp) has been isolated from Thymalin by reversed-phase high performance liquid chromatography. Pharmaceutical containing this agent (Thymogen) was designed on the base of synthesized dipeptide. A novel immunomodulatory dipeptide was synthesized and termed Vilon. Both natural and synthetic pharmaceuticals activated T-cell differentiation, T-cell recognition of peptide-MHC complexes, induced the changes in intracellular composition of cyclic nucleotides and cytokine [interleukin (IL-2), interferon (IFN)] excretion of blood lymphocytes. Synthetic dipeptides activated neutrophil chemotaxis and phagocytosis. They had no influence on antioxidant response in thymocytes in comparison with natural peptides. Thymalin and Thymogen were used in persons with chronic pathology and immune dysfunction. The results indicate that thymic peptides participate in the regulating mechanisms of inflammatory processes as cytokine antagonists and show the difference between natural and synthetic products. It is important for the drugs designed to prevent immune dysfunction development.