Human natural killer cell maturation defect supports in vivo CD56(bright) to CD56(dim) lineage development.

Two populations of human natural killer (NK) cells can be identified in peripheral blood. The majority are CD3(-)CD56(dim) cells while the minority exhibits a CD3(-)CD56(bright) phenotype. In vitro evidence indicates that CD56(bright) cells are precursors of CD56(dim) cells, but in vivo evidence is lacking.