<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A partially purified preparation isolated from the thymus and containing several peptides. Human Thymosin-Fraction 5 (TF-5) possesses immunopotentiating properties and can correct many of the immunological deficiencies resulting from the lack of thymosin function in animal models and in humans. This agent enhances the spontaneous natural killer activity of normal human large granular lymphocytes; exhibits additive effects with recombinant IFN-alpha in enhancing natural killer activity in vitro and; enhances IL2 production, IL2 receptor expression, and IFN-gamma production in mitogen-stimulated large granular lymphocytes. TF-5 may also modulate the secretion of some hypothalamic peptides and pituitary hormones, including prolactin and growth hormone. (NCI04)</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>