IL-6, but not TNF-α, increases plasma YKL-40 in human subjects

Abstract Plasma levels of YKL-40 are elevated in patients with systemic infection, inflammatory disorders and cancer. Both monocytes/macrophages, neutrophils, and cancer cells have the capacity to produce YKL-40, but the regulation during the inflammatory response is unknown. To study the possible role of interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α in the regulation of YKL-40 plasma levels, we included healthy men, who received either recombinant human (rh)IL-6 ( n  = 6), rhTNF-α ( n  = 8) or vehicle ( n  = 7) for 3 h. The plasma levels of IL-6 and TNF-α reached ∼150 and ∼18 pg/ml, respectively, during the infusions. Following the IL-6 infusion, the plasma level of YKL-40 increased from ∼30 to ∼57 ng/ml ( p