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Datasets  >  preclinical study dataset  >  Activation of DC by TLR and...

Activation of DC by TLR and iNKT cell agonists in vivo

preclinical study dataset

My laboratory obtained data from a continued analysis of the ability of invariant NKT (iNKT) cells to assist priming of antigen specific T and B cell responses. We have carried out three complementary lines of research:

1) We have demonstrated that activation of human DC by Toll like receptor ligands (TLR-L) modulates the lipid biosynthetic pathway, resulting in enhanced recognition of CD1d-associated lipids by iNKT cells.

2) We have clarified the mechanisms by which CD1d-restricted lymphocytes translate T cell receptor (TCR) recognition of lipids with similar group heads into distinct biological responses. Using a soluble iNKT TCR and a newly engineered antibody specific for alpha-galactosylceramide (alpha-GalCer)-human CD1d (hCD1d) complexes, we measured the affinity of binding of iNKT TCR to hCD1d molecules loaded with a panel of alpha-GalCer analogues and assessed the rate of dissociation of alpha-GalCer and alpha-GalCer analogues from hCD1d molecules. We have extended this analysis by studying iNKT cell synapse formation and iNKT cell activation by the same panel of alpha-GalCer analogues. Our results indicate the unique role of the lipid chain occupying the hCD1d F' channel in modulating TCR binding affinity to hCD1d-lipid complexes, the formation of stable immunological synapse, and cell activation. Our results indicate a general mechanism by which lipid-specific lymphocytes are capable of recognizing both the group head and the length of lipid antigens, ensuring greater specificity of antigen recognition.

3) We demonstrated that pathogen-derived signals to DC mediated via TLRs can be modulated by activated iNKT cells
(Hermans et al, 2007). DC maturation induced in vivo with any one of a variety of TLR ligands was greatly improved through simultaneous administration of the iNKT cell ligand alpha-galactosylceramide. DC isolated from animals treated simultaneously with TLR and iNKT cell ligands were potent stimulators of naive T cells in vitro compared with DC from animals treated with the ligands individually. Injection of protein Ags with both stimuli resulted in significantly improved T cell and Ab responses to coadministered protein Ags over TLR stimulation alone. Ag-specific CD8(+) T cell responses induced in the presence of the TLR4 ligand monophosphoryl lipid A and alpha-galactosylceramide showed faster proliferation kinetics, and increased effector function, than those induced with either ligand alone. Human DC exposed to TLR ligands and activated iNKT cells in vitro had enhanced expression of maturation markers, suggesting that a cooperative action of TLR ligands and iNKT cells on DC function is a generalizable phenomenon across species.

These studies highlight the potential for manipulating the interactions between TLR ligands and iNKT cell activation in the design of effective vaccine adjuvants.






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