Natural killer receptors in patients with lymphoproliferative diseases of granular lymphocytes

The most relevant criterion for recognizing chronic granular lymphocyte (GL) proliferations, defined as lymphoproliferative disease of GL (LDGL), has been historically based on the number of the proliferating cells displaying typical GL morphology. With the extensive development of immunological and molecular techniques, two major groups of LDGL have been recognized, one belonging to the T-cell and the other to the NK cell lineage. The recent definition of a series of receptors of NK cells (NKR) and the identification of the specific targets recognized has expanded our knowledge of the properties of these cells and the discrimination between functional reactive and pathological proliferations. Some of these receptors are expressed by GL of T-cell lineage, suggesting a possible involvement in the genesis of GL proliferation. Following an extensive description of NKR in humans, this review will summarize the recent data on phenotypic and functional characteristics of NKR expressed by proliferating GL in patients with LDGL, discussing their role in this disorder.