Role of human natural killer cells in health and disease

Abstract

Natural killer (NK) cells, the CD3- CD56+ CD16+ subset of peripheral blood lymphocytes, have long been known to be involved in non-major histocompatibility complex-restricted natural immunity to virally infected and malignant target cells. The association of abnormalities in NK cell numbers or functions with a broad spectrum of human diseases has been more clearly defined in recent years as a result of the improved knowledge of NK cell physiology and advances in monitoring of NK cell functions in health and disease. The ability to reliably measure changes in NK activity and/or numbers during the course of disease or response to treatment has focused attention on the role of the NK cell in disease pathogenesis. The improved understanding of NK cell deficiency in disease has opened a way for therapies specifically designed to improve NK cell function. The therapeutic use of biologic response modifiers capable of augmenting NK cell activity in vivo and of adoptive transfer of highly enriched, activated autologous NK cells in diseases such as cancer and AIDS is being evaluated. The importance of NK cells in health and the consequences of NK cell deficiency or excess are likely to be more extensively monitored in the future.

Impairment of natural killer (NK) cytotoxic activity in hepatitis C virus (HCV) infection

“…NK cells are a subset of lymphocytes distinguishable from T and B lymphocytes by their phenotype (CD3 -, CD16 þ , CD56 þ ), morphology and functional responses [10,11]. These cells represent between 5% and 15% of the mononuclear cell population, but in some organs, as in the liver, up to 45% of the lymphocyte population are NK cells [10][11][12].…”

“…Host defence against tumour cells and spontaneous lysis of virus-infected cells are the most prevalent functional roles attributed to NK cells [10,11]. These responses may be increased by stimulation with interferons-alpha (IFN-a), IFN-b and IFN-g, and IL-2 [10,11].…”

Stimulation of natural killer cells by homoeopathic complexes: An in vitro and in vivo pilot study in advanced cancer patients

“…The concept of immunotherapy by stimulation of NKCs has a strong potential if we consider the fact that only one NKC alone can destroy 27 cancer cells before its death. 25 Natural killer cells have a sophisticated mechanism of activating and inhibiting receptors that has evolved to regulate their activity. 26 Each substance may stimulate or suppress the stimulatory or inhibitory receptors of the NKCs and therefore can regulate their immune response.…”

Improving methods of assessing natural killer cell cytotoxicity

“…Morphologically identified as large granular lymphocytes, mature circulating NK cells have cell surface antigens CD16 and CD56, but not CD3. Natural killer cells comprise only a small proportion (5% to 15%) of the lymphocytes in peripheral blood (Whiteside and Herberman, 1994). They have a unique ability to recognize and kill a variety of targets including virus infected cells and numerous types of tumour cells (Wu and Lanier, 2003) without previous sensitization (Smyth et al, 2005;Trinchieri, 1989).…”

“…They have a unique ability to recognize and kill a variety of targets including virus infected cells and numerous types of tumour cells (Wu and Lanier, 2003) without previous sensitization (Smyth et al, 2005;Trinchieri, 1989). These cells defend against a wide range of human diseases (Whiteside and Herberman, 1994) and play an important role in tumour defence. Programmed to seek out specific targets on cancer cells that allow selective killing, NK cells are critical in the control of tumour growth and metastasis (Wu and Lanier, 2003).…”