"Licensed" to cross-prime

NKT cells play an important role in cross priming ― a process whereby infectious agents outside the cell are taken up, processed, and presented to a certain type of T cell in order to create an immune response which is effective against tumours. The work, published online in Nature Immunology this week, suggests that NKT cells could potentially be an important new player in vaccine design.

Cross-priming critically depends on three cell types coming together: dendritic cells, a licensing cell, and a cytotoxic T cell (CTL). Normally, dendritic cells cross-prime infectious agents via the intervention of T helper cells ― which are licensing cells. However Christian Kurts and colleagues have revealed a novel mechanism where this process is instead triggered by another cell type entirely ― the NKT cell. Following interaction with NKT cells, dendritic cells secrete a chemical signal, which specifically attracts certain CTLs to them, where they can then be activated.

Until now it has been puzzling how the three rare cell types needed in order for cross-priming to occur can all interact in time and space. The NKT-elicited release of a chemical signal from dendritic cells provides a neat solution to this puzzle. The importance of NKT cells revealed by this study suggests that any future vaccine may be more effective if these cells are factored into their design.