It is already known for some time that Treg cells can subdue an excessive immune response and the resulting inflammation. For example, injections with Treg cells prevented autoimmune diseases in mice. However, for Treg cell treatments one needs a large amount of these cells, which is not easy to realise. In the blood, there are just a few of them, and in vitro they are difficult to produce. Using mast cells, Treg cells could be easily produced in the laboratory in large quantities. "The mechanism that we discovered, could be the basis for a new way to handle allergies," says Hideaki Morita.