[iNKT cells, a friend or a foe for autoimmune disease and allergy?]

iNKT cells are a unique subset of CD1-restricted T lymphocytes that express T cell receptor (TCR) and some NK receptors. iNKT cells express an invariant TCRalpha chain composed of Valpha14-Jalpha18 segments in mice and Valpha24-Jalpha18 segments in humans associated with TCRbeta chains using a restricted set of Vbeta. iNKT cells recognize glycolipid antigens such as alpha-galactosylceramide (alpha-GC) presented by CD1d, non-pormorphic MHC class I-like molecule, and rapidly secrete large amounts of cytokines including IL-4 and IFN-gamma upon activation. Due to its potent ability to produce a variety of cytokines, iNKT cells are involved in a various kinds of immunoregulation. iNKT cells play a regulatory role in some disease models such as type I diabetes in NOD mice. In contrast, iNKT cells exaggerate the pathogenesis such as arthritis, allergic airway inflammation and atherosclerosis. In addition, iNKT cells are an attractive target for immunotherapy because several different synthetic glycolipid antigens to modify the function of iNKT cells are available. In this review, we examine the potential roles of NKT cells in the pathogenesis of a variety of diseases including autoimmunity , allergy, infection and cancer. Additionally, we discuss on the recent advances in glycolipid therapy for these disease models.