PVR and infection: Arguments that may point to an important role of NK cells in the natural history of cervical cancer are: a) NK cells can recognize and either destroy virally infected cells or control the infection via cytokines (IFN-gamma and TNF-alpha), b) HPV-associated cervical tumors frequently exhibit a reduction in MHC class I expression as an immune evasion strategy, c) NK cell receptor ligands (MICA and CD155) are differentially expressed during progression to cervical cancer [15,18,19].