NK cells have a prominent role in early virus control. Upon activation NK cells control infection either through the lysis of infected cells, or by release of antimicrobial cytokines. This latter function enables them to influence adaptive immune responses as well. NK cells survey their surroundings through numerous inhibitory and activating receptors – integration of these signals determines the activity of an NK cell. More recent data indicate that NK cells may even acquire memory-like function enabling them to respond differently upon recall challenge. The importance of NK cells in control of viral infection is best illustrated by the sheer number of viral evasion mechanisms. These mechanisms include regulation of apoptosis, interference with ADCC, modulation of cytokines and chemokines and function of APCs. Even more numerous are viral techniques dedicated to control of engagement of NK cell receptors. The viruses can downmodulate ligands for activating NK cell receptors, provide competitors and surrogates for cellular ligands, interfere with their translation or target the activating receptors directly.
Despite a remarkable increase in knowledge about relationship between NK cells and viruses there are still many outstanding issues. This review highlights recent progress and current understanding of most important viral immunosubversive mechanisms directed at NK cells with emphasis on receptor-ligand interactions and their impact on overall immunity.