NK Cell Missing-Self Recognition

Natural killer cells patrol tissue and decide, target by target, whether to kill — not by recognising a foreign antigen the way T cells do, but by weighing an inhibitory signal from self MHC class I against an activating signal from stress-induced ligands. This simulation renders a field of target cells, each with its own MHC-I and stress-ligand density, and lets one to three NK cells dock at each cell in turn, integrate the two signals against a tunable threshold, and either spare or kill it. Downregulate MHC-I across the population, or carve out an infected patch, and watch the kill decisions track the underlying biology: cells that lose their "self" signal get killed even though nothing foreign was ever displayed.