NK cells kill the viral infected cells due to:
Ans. (a) Increased expression of MHC class I molecules Features of target cell killing by NK cell: Inversely related to target cell expression of MHC class I molecule. So, it kills the cell that expresses little or no HLA class I molecule (provide immunosurveillance) such as virus infected cells, ceain tumor cells and allogenic cells. Non-immune, i.e. without previous sensitization, MHC unrestricted and non-antibody mediated. It kills host cell infected with intracellular bacteria, e.g. Mycobacteria, TB. Listeria, monocytogens. Do not kill cells which express class I MHC (all normal nucleated cells express it).
Increased expression of MHC class I molecules
Decreased expression of MHC class I molecules
Increased expression of MHC class II molecules
Decreased expression of MHC class II molecules