Regulation of immunity and pathogenesis in infectious diseases by CD1d-restricted NKT cells

CD1d-restricted NKT cells are emerging as an unusual lymphoid lineage with important immunoregulatory properties. To date, much of our understanding of the biology of the CD1/NKT system comes from studies that utilise non-natural glycolipid ligands. Recent evidence suggests that NKT cells play an important role in the response to pathogens, manifesting a range of functions including cytotoxicity, help for antibody formation and regulation of Th1/Th2 differentiation. Infectious disease models provide appropriate physiological and pathophysiological systems to explore the biological roles of this lineage in immunity and disease. Novel insights are emerging from infection models, particularly with respect to the nature of ligands recognised by the T cell receptor of NKT cells, and to the role of diverse non-T cell receptor NK activation and inhibitory receptors in regulation of the lineage. Such insights have the potential to add considerably to our understanding of the CD1/NKT cell system and to the immunology and pathogenesis of infectious diseases.