FCER's Internat Conference on Spinal Manipulation, 1991; 84–96
Graham, M.; Brennan, P.
Natural Killer (NK) cells are large granular lymphocytes readily distinguished from thymus derived (T) and bursa-equivalent (B) lymphocytes on the basis of cellular morphology, surface markers and function. Unlike T and B cells, NK cells have few azurophillic granules and a high cytoplasm-nuclear ratio. A further significant difference between NK cells and T and B cells is that NK cells are capable of responding to antibody-coated target cells, neoplastic cells and virally infected cells without prior sensitization (1). On their cell surfaces, NK cells express the specific cell surface antigens, CD16 and CD56 (NKH-1), with the CD56 marker being found on all activated NK cells (2). CD56 is normally expressed at low density on cells in peripheral blood but increases in expression are seen following in vitro growth and stimulation (3). Recent work by others suggests that the numbers of NK cells and their functional ability to lyse stimulating target cells is influenced by factors such as stress and illness. Low numbers or suppressed activity have been documented in patients suffering from chronic viral infections, arthritis, chronic headaches and clinical psychiatric depression (4). Although NK cells comprise a low percentage of circulating lymphocytes, they can be rapidly and accurately quantitated using flow cytometry and labelled monoclonal antibodies directed at specific cell surface antigens. In flow analysis, fluorescently-labelled single cells pass through a focused laser beam and are quantified on the basis of their light scattering properties. As each cell passes through the beam, it emits scattered and fluorescent light signals that are then collected and amplified in the photodector tubes. The signals provide information on cell size and granularity as well as cell surface markers (5). Previous work in our laboratory suggested that both the percentage and the absolute numbers of NK cells were significantly lower in patients presenting to the main clinic of The National College of Chiropractic (NCCC) than in asymptomatic controls (6). However, these results were obtained using conventional fluorescence microscopy. Using flow cytometry to quantitate cells and a standard cytotoxicity assay to measure cell function, we are currently assessing the numbers and functional ability of NK cells. The purpose is to develop sensitive cellular outcome measures for use in future clinical trials.
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