iNKT cells: innate lymphocytes with a diverse response.

It is now established that natural killer T (NKT) cells can influence adaptive immune responses by producing vast amounts of cytokines. Different subsets of NKT cells with distinctive functional characteristics regarding cytokine production have been described. This is the case for NKT1, NKT2, or NKT17 that resemble conventional CD4 Th1, Th2, and Th17 cells in the cytokines they produce. Unlike conventional CD4 T cells that mostly acquire functional specialization in the periphery, a number of NKT cells become specialized effectors during thymic development. This opinion article describes the evidence for an extrathymic commitment of specialized NKT-cell subsets that, together with thymic lineages, contributes to the overall functional diversity of NKT cells participating in immune responses in the periphery.