Historically, tissue transplantation, especially of refrigerated tissue (after filatov). It was theorised that non-specific substances, capable of initiating restorative processes, formed in tissues when refrigerated. This therapy has been discredited and outlawed in western medicine. Cell therapy (after niehans) refers to implantation of tissue by injection. Originally this involved fresh cells but later frozen or lyophilised cells. This therapy has also been banned in most countries but its illicit use is apparently widespread.