Reactive mast cells are the culprit in aller-gic diseases and have also been implicated in other diseases ranging from autoimmune disorders to cancer to atherosclerosis. These immune sentinel cells normally defend against parasites and bacteria, but some-times they overreact to harmless intruders, such as pollens or plant oils, releasing gran-ules loaded with inflammation-inciting mole-cules, such as histamine, as well as various proteases and cytokines that cause allergic and inflammatory reactions.Mast cell research has been hampered by its reliance on primary cultures of human or mu-rine mast cells. Establishing primary cultures is a costly, time-consuming affair that takes 6 to 8 weeks and yields a limited number of cells. A longtime milestone in allergy and in-flammatory medicine has been realized by a National Institute of Allergy and Infectious Diseases team, which developed a new mast cell line derived from human mast cell leu-kemia tissue. Named LAD2, this line closely resembles normal mast cells in the human body. The availability of this immortalized mast cell line ensures a continuous supply of human mast cells, yielding reproducible data that is more easily compared between different labs. The LAD2 cell line represents a potent tool for understanding the normal functions of mast cells within the human body and identifying the mechanisms of a variety of diseases. Research utilizing this cell line promises to lead to the development of novel therapies to combat allergic diseases. Since its avail-ability in 2001, the cell line has been made widely available to the research community via Material Transfer Agreements, resulting in more than 60 publications from laborato-ries worldwide. It has also been a licensing success, with the execution of more than 30 licenses with biotechnology and pharma-ceutical companies.With this cell line, scientists are analyz-ing the molecular mechanisms used by al-lergens and anti-inflammatory agents to aggravate or suppress mast cell activity. Projects include identifying the molecular mediators triggered by allergens, designing tests to identify new allergens, and devel-oping compounds to treat inflammations caused by mast cells. With this new human cell line, scientists can save time, effort, and expense to advance allergy and inflamma-