IMMUNOSTIMULATORY AGENT

There is disclosed an immunostimulatory agent comprising a peptide derived from lactoferrin having activity to modulate the release of inflammatory mediators from cells of the immune system. The peptide promotes the release of leukotriene B4 from polymorphonuclear neutrophils induced by activators such as the calcium ionophor A23187. It also promotes the release of histamine from mast cells induced by activators such as .alpha.-toxin- producing Staphylococcus aureus cells or the calcium ionophor A23187. The peptide is effective at low concentrations within the range of 1 to 100 ppm. By promoting the release of such inflammatory mediators the peptide can potentiate the cellular immune response and stimulate the host defense against infectious disease. This newly discovered immunostimulatory agent is useful as an active component of pharmaceuticals, hygiene products, clinical foods, etc., for prevention and treatment of bacterial, fungal, and viral infections in humans and animals.