ABSTRACT
CD1e is a member of the CD1 family that participates in lipid antigen presentation without interacting with the T-cell receptor. It binds lipids in lysosomes and facilitates processing of complex glycolipids, thus promoting editing of lipid antigens. We find that CD1e may positively or negatively affect lipid presentation by CD1b, CD1c, and CD1d. This effect is caused by the capacity of CD1e to facilitate rapid formation of CD1-lipid complexes, as shown for CD1d, and also to accelerate their turnover. Similar results were obtained with antigen-presenting cells from CD1e transgenic mice in which lipid complexes are assembled more efficiently and show faster turnover than in WT antigen-presenting cells. These effects maximize and temporally narrow CD1-restricted responses, as shown by reactivity to Sphingomonas paucimobilis-derived lipid antigens. CD1e is therefore an important modulator of both group 1 and group 2 CD1-restricted responses influencing the lipid antigen availability as well as the generation and persistence of CD1-lipid complexes.
Subject(s)
Antigens, CD1/immunology , Immunity/immunology , Lipids/immunology , Animals , Antigen Presentation/immunology , Clone Cells , Dendritic Cells/immunology , Glycolipids/immunology , Glycoproteins/immunology , Gram-Negative Bacterial Infections/immunology , Humans , Kinetics , Mice , Mice, Transgenic , Natural Killer T-Cells/immunology , Sphingomonas/immunologyABSTRACT
T lymphocytes expressing the T cell receptor (TCR)-gammadelta recognize unknown antigens on tumor cells. Here we identify metabolites of the mevalonate pathway as the tumor ligands that activate TCR-gammadelta cells. In tumor cells, blockade of hydroxy-methylglutaryl-CoA reductase (HMGR), the rate limiting enzyme of the mevalonate pathway, prevents both accumulation of mevalonate metabolites and recognition by TCR-gammadelta cells. When metabolite accumulation is induced by overexpressing HMGR or by treatment with nitrogen-containing bisphosphonate drugs, tumor cells derived from many tissues acquire the capacity to stimulate the same TCR-gammadelta population. Accumulation of mevalonate metabolites in tumor cells is a powerful danger signal that activates the immune response and may represent a novel target of tumor immunotherapy.
