Immunoregulation via 'bystander suppression' needs minute amounts of substances - a basis for homeopathic therapy?

One of the main characteristics of homeopathic drugs is the low concentrati on of substances they contain. In most discussions this serves as the predo minant argument against homeopathic treatments. The small amount of ingredi ents is in most instances considered not to be able to induce significant c hanges in classical pharmacological models. A few years ago researchers at the Harvard Medical School in Boston observed that the auto-reactivity of T -cells is managed by the immune system in at least two different ways that obviously were dependent upon the concentration of the antigen they encount er: If they see high concentrations of a self-antigen they are deleted (kil led), but when given low doses they undergo a special kind of active inhibi tion (called 'bystander suppression'). We feel that this type of regulation induced by very low substance concentrations could serve as a model to exp lain the way in which at least some homeopathic pharmaceuticals mediate the ir therapeutic effects. (C) 2000 Harcourt Publishers Ltd.