Which marker is specifically used to identify Natural Killer cells?

Natural Killer (NK) cells are a unique subset of lymphocytes that play a critical role in the innate immune system, primarily in the recognition and elimination of virus-infected cells and tumor cells. The surface marker specifically used to identify NK cells is CD56. This marker is typically expressed at high levels on NK cells, distinguishing them from other lymphocytes, such as T cells and B cells.

CD3 is associated with T cells, serving as a core component of the T cell receptor complex, and is not present on NK cells. CD4, on the other hand, is a marker found on helper T cells but not on NK cells. CD19 is a pan-B cell marker, used to identify B lymphocytes, not NK cells. Therefore, CD56 stands out as the definitive marker for identifying Natural Killer cells in immunological studies.