Glycolipids With Nonreducing End Alpha-Mannosyl Residues That Have The Potential To Activate Invariant V Alpha 19 Nkt Cells

We have previously demonstrated that alpha-mannosyl ceramide and its derivatives promote immune responses of NK1.1(+) invariant V alpha 19-J alpha 33 T cell receptor (TCR) alpha(+) T cells (V alpha 19 NKT cells). In this study, attempts were made to determine the structural requirements for natural ligands for V alpha 19 NKT cells. Naturally occurring and synthetic glycolipids were analyzed for their ability to stimulate the cells prepared from invariant V alpha 19-J alpha 33 TCR transgenic mice, in which development of V alpha 19 NKT cells is facilitated. As a result, alpha-mannosyl phosphatidylinositols such as 2,6-di-alpha-mannosyl phosphatidylinositol and alpha-mannosyl-4 alpha-glucosaminyl-6-phosphatidylinositol (alpha-Man-GlcNH(2)-PtdIns) as well as alpha-mannosyl ceramide derivatives were found to activate the cells from the transgenic mouse liver, gut lamina propria and spleen in vivo and in vitro. Thus, glycolipids with nonreducing end alpha-mannosyl residues are suggested to be potent antigens for V alpha 19 NKT cells. Next, a series of invariant V alpha 19-J alpha 33 TCR+ hybridomas, each with variations in the sequence of the V alpha-J alpha junction and the TCR beta chain, were tested for responsiveness toward the alpha-mannosyl glycolipids. A loose correlation between the primary structure of the TCR and the reactive glycolipids was observed. For instance, hybridomas expressing TCRs consisting of an alpha chain with a variation in the V alpha 19-J alpha 33 junction and a V beta 6(+)beta chain showed affinity towards alpha-mannosyl ceramide and alpha-Man-GlcNH(2)-PtdIns, whereas those expressing TCRs with an invariant V alpha 19-J alpha 33 alpha chain and a V beta 8(+)beta chain responded to 2,6-di-alpha-mannosyl phosphatidylinositol. Thus, it is suggested that V alpha 19 NKT cells with microheterogeneity in the TCR structure have been generated for defense against various antigens expressing alpha-mannosyl glycolipids.