Keyhole limpet hemocyanin (KLH) is a large cooper-containing protein consisting of subunits with MW of 400 kDa. It is found in the hemolymph of the sea molluskMegathura crenulata. This?extracellular respiratory protein?has many immunostimulatory properties, including the ability to enhance the host’s immune response by interacting with T cells,?monocytes, macrophages, and polymorphonuclear lymphocytes. Since its discovery, KLH has been used primarily as a carrier for vaccines and antigens and as adjuvant treatment in regimens such as antimicrobial therapy.