【Abstract】Objective To test the cytokine-inducing substance (CIS) permeability of a new kind of dialyzer-Syntra 160 in vitro dialysis with whole human donor blood. Methods The dialyzers used in these tests were high-flux polyethersulfone dialyzers. Bicarbonate dialysate (D) was contaminated by Pseudomonas. aeruginosa (P.A) culture filtrate, and cytokine production in the peripheral blood mononuclear cells (PBMC) expressed as pg/2.5×106 was used as the indicator of transmembrane passage of CIS. Whether the CIS can pass through the dialysis membrane to the blood side was investigated under several conditions, including D contaminated with different dilution of bacterial culture filtrate (10-2, 10-3, 10-4)。 Results The total production of all TNF-α was not detectable in the PBMC sample harvested from blood before exposure to dialyzer (B0), after 15 min circulating the whole blood with uncontaminated bicarbonate D (B15), 60 min after circulating the CD with 10-2, 10-3,10-4 diluted bacterial culture filtrate (B60) and 60 min after the both blood and contaminated D keeping in still condition (B60S). While the TNF production in the 10-2,10-3,10-4 diluted bacterial culture filtrate CD (CD0), the TNF-α production were 477.0±260.7, 318.9±49.3, 102.6±77.0. The IL-1Ra production in the group of Dcontaminated by 10-2 diluted bacterial culture filtrate was 156.8±81.6 in B0, 188.9±108.8 in B15, 271.2±127.4 in B60, 2971.8±1123.0 in D0. In the group of D contaminated by 10-3 diluted bacterial culture filtrate, the IL-1Ra in B0, B15, B60, D0 was 201.2±154., 143.9±72.7, 208.7±99.7, 2274.0±925.9. In the group of D contaminated with 10-4 diluted bacterial culture filtrate, the IL-1Ra value in B0, B15, B60, D0 value was 116.3±40.5, 127.8±60.8, 111.7±18.5, 1175.5±603.0. There was no significant difference among the blood sample among B15, B60 and B0, but the cytokine production in D0 was much higher than any other group, the difference was significant. Conclusion The Syntra 160 can effectively prevent the passage of cytokine-inducing substance from highly contaminated D under very critical condition. 