Figure 1. The prototypical mature NK-cell lytic synapse.

The mature natural killer (NK)-cell lytic synapse is defined by the formation of a supramolecular activation cluster (SMAC) at the interface between the NK-cell and target cell to which lytic granules polarize. The prototypical version of this synapse contains a central SMAC (cSMAC) that includes a secretory domain through which lytic granules may traverse. The series of images show a YTS human NK cell expressing a CD2-GFP (green fluorescent protein) fusion protein making contact with an EBV-transfomed B-cell line. The cell-cell conjugates were fixed, permeabilized and evaluated for the presence of perforin (red) using a monoclonal antibody. Perforin is contained within lytic granues and is presented as a surrogate for them, while CD2 patterning under normal conditions parallels F-actin at the mature synapse.¹² Serial images were obtained using a confocal microscope through the z-axis and the three-dimensional cell volume reconstructed in silico. The individual images on the left from top to bottom demonstrate a 180-degree rotation around the z-axis (Scale bar=5μM) The schematic on the right displays the position of the NK cell (yellow) and B cell (blue), CD2 at the SMAC (green) and perforin at the SMAC (red) in each image. Also see an interactive version in online Supplementary Figure 1.