Molecular biology of NK T cell specificity and development

NK T cells recognize a glycosphingolipid, alpha -galactosyl ceramide, presented by CD1d. CD1d is capable of binding a variety of lipids, however, and the hydrophilic groups of the antigen contribute relatively little to CD1d binding. Amino acids in the CD1d groove and the top of the alpha helices are involved in lipid antigen presentation, suggesting a conventional mode of presentation and antigen recognition. NK T cells also have unique requirements for their differentiation, as suggested by the analysis of a number of mouse germline mutations. For example, the development of NK T cells, unlike conventional T lymphocytes, is highly lymphotoxin dependent.