Abstract: Tripeptides having general formula II Glu-Lys-Arg in which: Glu is a glutamic acid residue, Lys is a lysine residue and Arg is an arginine residue are described. The aminoacids composing the tripeptides of the invention may be either of the natural, L-series or of the D-series or a racemic mixture of the two said series, but the aminoacids are preferably selected from the L-forms even though D- or DL aminoacids may also be considered. The invention refers also to the process for the preparation of said peptides as well as to their use as immunostimulant agents.

Abstract: Thymolymphotropin, a thymus derivative able to stimulate the differentiation and the function of T-lymphycytes, is active after oral administration and can be prepared through a process of partial acid lysis of mammal thymuses. Pharmaceutical compositions containing thymolymphotropin are utilized in the treatment of primary and secondary immunodeficiencies.