Natural Killer (NK) cells constitute up to 15% of all white cells in the peripheral blood and a small proportion of cells in the normal bone marrow. However they cannot be readily distinguished morphologically from other lymphocytes and identification relies on flow cytometric analysis.
Typically the NK cell has the appearance of a large granular lymphocyte, Figure 1, which has an eccentric mature nucleus, abundant cytoplasm and coarse azurophilic granules. These cells are derived from the hematopoietic stem cell, then the T/NK cell progenitor at which stage they diverge and become committed to the NK lineage. They acquire some common T lineage antigens, CD2 and CD7, but are negative … Read more »