Natural killer T cells restricted by the monomorphic MHC class 1b CD1d1 molecules behave like inflammatory cells

Murine V alpha 14(inv)T cells (NKT cells), restricted by the CD1d1 MHC 1b molecules, are a distinctive subset of T cells endowed with pleiotropic functions. CD1d1-restricted NKT cells infiltrate the granulomas induced by the s.c. injection of mycobacterial phosphatidylinositoldimannoside (PIM2) but not of its deacylated derivative. NKT cells are detectable as early as 6 hours following the injection. Although the molecular structure of PIM2 meets the requirements for presentation by CD1d1, Ab blocking and adoptive transfer experiments of wild-type NKT cells into CD1d1(-/-) mice show that CD1d1 expression is not required for the early recruitment of NKT cells to the injection site. This conclusion was confirmed by the finding that IL-12R beta (-/-) and CD40(-/-) mice were able to recruit NKT cells after PIM2 challenge. Moreover, the injection of alpha -galactosylceramide, an NKT cell ligand that is recognized in the context of CD1d1, promoted only a minor recruitment of NKT cells. By contrast, injection of beta -galactosylceramide, a synthetic glycolipid that binds to CD1d1 but does not activate the CD1d/TCR pathway, resulted in the development of large granulomas rich in NKT cells. Finally, local injection of TNF-alpha mimics the effect of glycolipids. It is concluded that NKT cells migrate to and accumulate at inflammatory sites in the same way as other cells of the innate immune system and that migration to and accumulation at inflammatory sites are processes independent of the CD1d1 molecule.