First line of defence against tumor and virus?

Ref: Robbins review E-Book, P 67* NK cells have the ability to respond without prior sensitization.* They carry receptors for MHC class I molecules which inhibit their lytic function. When expression of class I MHC molecules is reduced on a cell surface by viral interference, inhibitory receptors on NK cells do not receive a negative signal and the targeted cells is destroyed.* NK cells have CD16, Fc receptor that allows them to bind to opsonized cells and lyse them. This is a form of type II hypersensitivity with antibody mediated disease.