Human Normal Peripheral Blood CD56+ NK Cells

Human CD56+ Natural Killer (NK) cells are critical cytotoxic effector lymphocytes of the innate immune system, playing an essential role in eliminating infected or tumorigenic cells. They are characterized by the presence of CD56 protein (also known as NCAM) on their surface, which serves as a marker for NK cell identification. Key Characteristics and Functions: Innate Immune System: NK cells are always ready to respond to threats, unlike adaptive immune cells that require prior exposure to specific pathogens. This allows NK cells to act quickly during early stages of infection or tumor development. Role of MHC I in NK Cell Activation: MHC I (Major Histocompatibility Complex I) molecules on the surface of healthy cells generally act as inhibitory signals for NK cells, preventing them from attacking normal, healthy tissue. When target cells lose or downregulate MHC I expression (a common feature in tumor cells and virus-infected cells), the inhibitory signal is diminished. Ho