W150 - Natural Killer Cells may be Functionally Altered due to Simulated Microgravity Exposure

Immune dysregulation has been reported due to spaceflight, including impacts on Natural Killer (NK) cell function. As cytotoxic cells of the innate immune system, NK cells target virus-infected and malignant cells. NK cells are an important cell type to study in this context, given the increased risk of cancer development in deep space missions due to radiation exposure, and reported viral reactivation during spaceflight. Microgravity is the condition of “weightlessness” due to low gravitational forces in the space environment and may contribute to the reported changes in astronaut immune function. Here, we cultured the NK92 cell line in simulated microgravity (SMG) for 72 hours. Our preliminary results indicate a 12.8% and 8.0% decrease in NK cytotoxicity against K562 and MCF7 cancer cell lines, respectively. Interestingly, we measured a 32.3% and 27.0% increase in mRNA expression of cytotoxic molecules, perforin and granzyme B. Our secretory data of these molecules indicate a 13.5% decrease in perforin secretion, coupled with a 209% increase in granzyme B secretion. Taken together, our preliminary results suggest that NK cells may be functionally altered due to exposure to simulated microgravity. The measured decrease in cytotoxicity after SMG exposure may be preceded by 1) dysregulation of the NK cell degranulation process and/or 2) NK-target cell interactions. Our next steps will focus on these parameters. Understanding the effects of microgravity exposure will become increasingly important as astronauts complete future deep space missions. This research also has the potential to inform us about age-related immune dysregulation experienced on Earth.