NK cell activity and IL-6 measurement
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BLOOD
Blood samples for measuring inflammatory and immunologic markers (interleukin [IL]-6, natural killer [NK] cell activity) were collected at baseline (preoperative) and 24 h after surgery.A blood test kit (NK Vue® Kit, ATGen, Sungnam, Republic of Korea) was used to measure NK cell activity. Briefly, a 1 ml sample of whole blood was transferred into a specific tube for the NK cell activity test, containing a patented stimulatory cytokine (Promoca™, ATGen, Sungnam, Republic of Korea). The collection tube was repeatedly and gently mixed; within 30 min of collection, the tube was incubated for approximately 22 h in a 37 °C chamber, according to the manufacturer’s instructions. The stimulatory cytokine produces interferon-γ into the plasma during the incubation period; this secretion predominantly occurs via NK cells rather than innate adaptive immune cells [