Tumor necrosis factor ( TNF ) and interleukin ( IL ) -6 concentrations were measured by radioimmunoassays ; IL-8 concentrations by an enzyme-linked immunosorbent assay ( ELISA ) and pentoxifylline concentrations by high-performance liquid chromatography at 0 , 3 , 6 , 12 , 18 , 24 and 48 hrs after study entry .
