Romurtide (Muroctasin) is a non-specific immune stimulant derived from muramyl dipeptide, which is obtained from gram-positive bacterial cell walls. Muroctasin stimulates macrophages, which release interleukin-l, which in turn increases production of colony-stimulating factors; muroctasin also evokes an increased production of neutrophils. It is used in Japan for chemotherapy-induced leukopenia.