DC/IL-18 polarizes toward interacting NK cells. (A) Confocal microscopy analysis of perforin (red) and IL-18 (green) in an iDC/NK conjugate after 3 hours of interaction. Insets shows details of single and double fluorescence at the immunologic synapse. Arrowheads indicate perforin; arrows, IL-18. One representative experiment of 4 performed is shown. (B) Western blot analyses with anti-IL-18 (lanes 1 and 2) or anti-cathepsin D (CD; lanes 3 and 4) of 3-hour supernatants of iDCs cultured alone (iDCs; lane 1 and 3) or with NK cells (NK/iDCs; lanes 2 and 4). Arrows point to the precursors and mature forms of the 2 proteins. One experiment of 10 performed is shown.