Subsets of Human Peripheral Blood Natural Killer Cells

In human peripheral blood, natural killer (NK) cells represent a small lymphocyte subset which can be delineated through the expression of very selective markers such as CD16 or NKH1. This subset, which accounts for approximately 10% of circulating lymphocytes, is heterogeneous and overlaps with previously defined T lymphocyte subpopulations expressing surface structures such as CD2, CD3, or CD8. A precise dissection of NK cell heterogeneity has been achieved using cloning techniques. Cloned NK cells can be operationally divided into three groups depending upon the expression of CD2 and CD3 molecules (CD2 – CD3 – NKH1 + , CD2 + CD3 – NKH1 + , and CD2 + CD3 + NKH1 + ). The minor populations of NK active lymphocytes which express CD3 appear to use T cell receptor structures to recognize on targets non-MHC determinants, perhaps activation antigens. Recognition structures employed by the majority of NK cells (CD2 + CD3 – NKH1 + ) are still unknown.