Figure 2.

NK cell Surveillance of Cancer Cell (A) The presence of inhibitory signals and lack of activating signals prevents the activation of the NK cells which avoids the lysis of the healthy cells. (B) NK cell recognizes the cancer cell due to the lack of human leukocyte antigens (HLAs) and/or other inhibitory ligands on cancer cell (“missing-self hypothesis”), which results in production of cytokines, granzyme B and perforins that leads to the cancer cell killing. This scenario is simplified. Activation signals are still necessary to induce activation as the absence of inhibitory signals alone is usually insufficient. (C) NK cell is activated via the activating signals and the engagement with the activating ligands on the cancer cell in the lack of inhibitory signals, which leads to the production of perforins and granzyme B and cytokines, which ultimately yields cancer cell killing. Figure created with BioRender.com.