Fig. 3

A, B NK cells mechanism of actions for cytolytic purpose. NK cells employ multiple mechanisms of action to exert their cytolytic function against target cells. These mechanisms involve a coordinated interplay of activating and inhibitory signals, leading to target cell recognition, activation, and destruction. The primary mechanisms of NK cell-mediated cytotoxicity include: (1) Release of Cytotoxic Granules, (2) Death Receptor Pathway, and (3) ADCC. C Viral mechanisms for evading NK cell: (1) Elevating the levels of inhibitory ligands (including HLA-E and HLA-C) and decreasing the presence of activating ligands (including ULBP1, ULBP2, MIC-A MIC-B) on the infected cell. (2) Viral products or cytokines released from infected cells have the ability to alter the quantity of receptors on NK cells. This alteration involves an increase in the expression of inhibitory receptors such as NKG2A and a decrease in the expression of activating receptors such as NKG2D on the infected cell. (3) Several viruses have the ability to directly disrupt the functioning of NK cells by infecting them. Viral infection can induce immune suppression, either by suppressing the cytotoxic function of NK cells or by initiating apoptosis, resulting in the depletion of NK cells