Natural killer (NK) cells are a subset of cytotoxic lymphocytes of the innate immune system, which have important role in early defense against transformed and virus-infected cells. After recognition of an appropriate target cell, an immunological synapse is formed between the NK cell and the recognized target cell, followed by clustering the cytotoxic granules around the microtubule-organizing center (MTOC). The main components of cytotoxic granules, perforin and the granzymes, are then released from the NK cells, resulting in apoptosis of the target cell.

Glucosamine is a component of natural polysaccharide mixtures. It is used extensively for the management of pain in osteoarthritis, but was observed to affect different cellular processes. For example, it has long been known that glucosamine effects NK cells activity, but the mechanism of action is still unknown. In order to analyze the cytotoxic process, we investigated the NK-92 cell line that possesses strong cytotoxic activity against the K562 cell line. We analyzed cytotoxicity of direct co-culture of NK-92 and K562 cells by flow cytometry, using two labelling dyes, DiOC18 to distinguish cells, and propidium iodide to detect dead cells. For activation of NK-92 cells we used different concentrations of interleukin 2 (IL-2). We showed that high concentration of IL-2 in the cell’s growth media transiently increase the ERK phosphorylation. ERK phosphorylation was accompanied by polarization of granules with perforin towards the immunological synapse. In order to study the impact of glucosamine on migration of granules, NK-92 cells were pre-treated with different concentrations of glucosamine. A dose-dependent decrease in cytotoxicity of NK-92 towards K562 cells was observed. Moreover, localization of perforin migration showed that addition of glucosamine to the medium induced redirected traffic of granules, disabling cytotoxicity towards the target cells. In addition, glucosamine was found to change dynamics of ERK phosphorylation.