Cluster of differentiation in NK cell

In humans, there are several stages of NK development in the bone marrow, which are based on the expression levels of CD34, CD117, CD56 and CD94. These phenotypes are restricted to the bone marrow and are not found in lymph nodes, spleen or peripheral blood. NK maturation begins with the expression of CD56 followed by simultaneous expression of CD94/NKG2A. Final NK maturation in the bone marrow correlates with a reduction in CD94/NKG2A expression and a CD56 low phenotype. It has been proposed that stage 2 cells, which are precursor NK cells, can traffic to lymphnodes, spleen and peripheral blood where they can undergo further but restricted maturation. Further details of marker expression during the different stages of development can be seen in table 1. NK cell developmental stages in human bone marrow. Also crucial to the development of NK cells from common precursors is the expression of CD122.