Les liaisons dangereuses: immunological synapse formation in animals and plants

The immunological synapse in vertebrates describes a specialized junction between a T cell and a target cell, enabling execution of immune responses through focal secretion. Recent insights in the plant immune system suggest that plant cells assemble a pathogen-inducible machinery at the cell surface that shares several features with the immunological synapse. Apparent mechanistic commonalities include co-stimulatory non-self alarm signals as triggers, cell polarization driven by actin cytoskeleton remodeling, protein concentration into ring-shaped assemblies at the cell periphery and focal exocytosis mediated by soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) proteins that are core factors for vesicle fusion. Although in plants, execution of immune responses by polar secretion seems to be a cell type–independent property, its confinement to T cells in the vertebrate immune system might reflect a greater division of labor.