Administration of NKT cell ligands did not induce any manifestations of autoimmunity (data not shown). their ability to trigger NKT FLLL32 cells, they displayed pronounced variations when coinjected with environmental providers or TLR ligands. Individual NKT ligands differed in their ability to prevent or break tolerance induced by low-dose mercury treatment. Similarly, different NKT ligands either dramatically potentiated or Rabbit Polyclonal to RPL26L inhibited the ability of TLR9 agonistic oligonucleotides to disrupt tolerance to mercury. Our data suggest that these variations could be mediated from the changes of cytokine profiles and regulatory T cell figures. Autoimmune diseases can arise because of complex relationships between genetic and environmental factors. The heavy metal mercury, in addition to being a common environmental pollutant, is found in a wide range of commercial and medical products, allowing for accidental or occupational exposure. In humans, chronic exposure FLLL32 to low doses of inorganic mercury, a potent immunomodulator (1), can induce glomerulonephritis and proteinuria (2,3), excessive T cell activation, improved levels of serum IgE, and anti-nuclear Abs in the FLLL32 serum (4,5). A similar immune dysfunction can be induced in mice wherein administration of subtoxic doses of HgCl2to vulnerable animals induces an autoimmune syndrome characterized by raises in serum Igs and anti-nucleolar autoantibody (ANoA)3production (6,7). Mercury-induced ANoA production depends on the MHC haplotype, with the H-2sand H-2bgene products conferring susceptibility and resistance, respectively (8). In addition, susceptibility is definitely affected by unidentified background genes, with varying susceptibility between different mouse strains. A.SW mice (H-2s) are very vulnerable; C57BL6-SJL (H-2s) mice are less so, whereas additional strains like DBA/2 (H-2d) are completely resistant (911). The mechanisms by which a heavy metal disrupts immune tolerance and induces autoimmunity remain unknown. NKT cells are evolutionarily conserved lymphocytes expressing NK and T cell lineage markers. Classical or type 1 NKT cells carry a semiinvariant TCR that recognizes a variety of glycolipid Ags offered by CD1d, a nonpolymorphic MHC class I-like Ag-presenting molecule (1214). These cells carry the hallmarks of memory space T cells, secreting a burst of cytokines (including IFN-, IL-4, IL-13, IL-10, and TGF-) within hours of encountering their Ags (14,15). This, combined with the up-regulation of costimulatory molecules like CD40L (12,15), results in rapid activation of the immune system, making this cell type a very potent modulator of an immune response. The ligand most commonly used to activate these cells is definitely a marine sponge-derived glycolipid, -galactosyl ceramide FLLL32 (-GalCer) (12). We used two recently developed synthetic FLLL32 variants of -GalCer, PBS 57 (16) and 4-deoxy -GalCer (17), to study the effects of NKT cell activation on mercury-induced autoimmunity. Recent studies have shown that NKT cells form an important part of the innate immune defense against a variety of microbes. The most potent microbial NKT cell ligands were recognized on Gram-negative, LPS-negative users of theSphingomonasspecies, indicating that this cell subset is definitely a major innate acknowledgement pathway for LPS-negative bacteria (18). The development or exacerbation of autoimmunity has been linked separately to exposure to infectious providers (6) or chemicals (6,19,20). We investigated the combined effect of a chemical, mercury, and a NKT cell ligand-bearing bacterium of theSphingomonasspecies,Sphingomonas capsulata(18), within the development of autoimmunity. Vulnerable mice can be tolerized to mercury by pre-exposing them to low levels of the heavy metal under nonactivating conditions (our unpublished observations). We examined whether NKT cell activation experienced regulatory functions in the induction or maintenance of tolerance to mercury. We demonstrate that, overall, NKT cell activation can exacerbate the mercury-induced syndrome. Bacteria bearing both NKT and TLR ligands strongly exacerbated the weighty metal-induced autoimmunity. However, the two synthetic NKT cell activators, when combined with two additional immunomodulatory providers, mercury and a TLR9 agonist, exerted profoundly different effects. Only one of the ligands prevented induction of tolerance to mercury,.