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. Author manuscript; available in PMC: 2012 Dec 1.
Published in final edited form as: Curr Opin Virol. 2011 Dec 1;1(6):497–512. doi: 10.1016/j.coviro.2011.10.017

Figure 3. Two potential mechanisms for losing inhibitory signals from KIR receptors.

Figure 3

NK cells are regulated by a balance between activating and inhibitory receptors. In health this balance favors inhibition of NK cells, because the inhibitory signal dominates the activating signal. During viral infections the inhibitory signal derived from MHC class I may be lost by down-regulation of cell surface MHC class I, thus favoring NK cell activation: “Missing-self model”. However multiple mechanisms exist to change the peptide repertoire of cell surface MHC class I. If this change favors presentation of weak inhibitory “antagonist” peptides then these peptides can efficiently disrupt the inhibitory signal due to strong and intermediate inhibitory peptides, and thus also favor NK cell activation: “Altered-self model”.