Dendritic cells play a vital role in regulating the immune response. They are the only cells capable of activating T cells that have not previously been exposed to a particular antigen (immune threat) to recognize and mount an attack on these foreign proteins. This process ensures an appropriate immune response against potentially harmful antigens. Dendritic cells are also thought to have the ability to instruct the immune system to ignore certain antigens, establishing a state of immune tolerance in the body. When the balance between immune activation and immune tolerance is disrupted, the result may be the development of autoimmune disorders in which the immune system attacks body tissue or cancer in which tumour cell growth goes unchecked. Dr. Cheryl Helgason is studying the biology of dendritic cells and the mechanisms by which they interact with T cells to activate an immune response or to establish immune tolerance. Such research could suggest ways of manipulating immune function to develop new methods of treating cancers, autoimmunity and other diseases involving immune dysfunction.