Molecular weight estimate of fibrin induced IL-8 by gel filtration chromatography. The 24-hour fibrin conditioned media were concentrated 20× by lyophilization, and fractionated by applying to a gel filtration P-30 column which has a fractionation range between 2.5 to 40 kD. The column was previously calibrated with protein standards. Samples were eluted under physiologic salt and pH conditions. Protein concentration was determined by spectrophotometer at 280 nm and IL-8 antigen was assayed by RIA from each fraction. The result was expressed as mean of IL-8 ng/mL ± SD of a duplicate sample and was representative of 2 separate experiments. One major IL-8 peak appeared with molecular weight range between 6,500 to 29,000 d.