{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T11:37:22Z","timestamp":1773401842100,"version":"3.50.1"},"reference-count":78,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2021,6,23]],"date-time":"2021-06-23T00:00:00Z","timestamp":1624406400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec><jats:title>Background<\/jats:title><jats:p>The coronavirus-19 disease (COVID-19) pandemic reminds us of the importance of immune function, even in immunologically normal individuals. Multiple lifestyle factors are known to influence the immune function.<\/jats:p><\/jats:sec><jats:sec><jats:title>Objective<\/jats:title><jats:p>The aim was to investigate the association between NK cell activity (NKA) and multiple factors including vitamin D, physical exercise, age, and gender.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>This was a cross-sectional association study using health check-up and NKA data of 2,095 subjects collected from 2016 to 2018 in a health check-up center in the Republic of Korea. NKA was measured using the interferon-\u03b3 (IFN-\u03b3) stimulation method. The association of NKA with 25-(OH)-vitamin D (25(OH)D) and other factors was investigated by multiple logistic regression analysis.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The average age of subjects was 48.8 \u00b1 11.6 years (52.9% of subjects were female). Among 2,095 subjects, 1,427 had normal NKA (NKA \u2265 500 pg IFN-\u03b3\/mL), while 506 had low NKA (100 \u2264 NKA &amp;lt; 500 pg\/mL), and 162 subjects had very low NKA (NKA &amp;lt; 100 pg\/mL). Compared to men with low 25(OH)D serum level (&amp;lt; 20 ng\/mL), vitamin D replete men (30\u201339.9 ng\/mL) had significantly lower risk of very low NKA (OR: 0.358; 95% CI: 0.138, 0.929; <jats:italic>P<\/jats:italic> = 0.035). In women, both low exercise (OR: 0.529; 95% CI: 0.299, 0.939; <jats:italic>P<\/jats:italic> = 0.030) and medium to high exercise (OR: 0.522; 95% CI: 0.277, 0.981; <jats:italic>P<\/jats:italic> = 0.043) decreased the risk compared to lack of physical exercise. Interestingly, in men and women older than 60 years, physical exercise significantly decreased the risk. Older-age was associated with increased risk of very low NKA in men, but not in women.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>Physical exercise and vitamin D were associated with NKA in a gender- and age-dependent manner. Age was a major risk factor of very low NKA in men but not in women.<\/jats:p><\/jats:sec>","DOI":"10.3389\/fimmu.2021.594356","type":"journal-article","created":{"date-parts":[[2021,6,23]],"date-time":"2021-06-23T06:21:45Z","timestamp":1624429305000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":29,"title":["Vitamin D and Exercise Are Major Determinants of Natural Killer Cell Activity, Which Is Age- and 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