153 Background: Interleukin-1 takes part in the immune response mediating acute cellular rejection after liver transplantation. The naturally occuring inhibitor of IL-1 activity has been found to be a secreted molecule known as IL-1 receptor antagonist (IL-1ra) capable of blocking the IL-1 receptor without resulting in signal transduction. The aim of this study was to investigate the value of IL1-ra secretion in serum and peritoneal fluids in comparison with common markers for acute graft rejection. Patients and methods: 13 children (median age = 11mo) were followed in the first two weeks after orthotopic liver transplantation. Serum and drainage fluids samples were daily obtained for IL-1ra, IL-2r, IL-15, sTNFr2 and IL-6 quantification (immunoassay). In case of acute cellular rejection (biopsy proven) IL-1ra levels were correlated to elevation of liver enzymes, αGST and different cytokines. Results: 3 children were found to have acute cellular rejection and had significant elevation of serum liver enzymes, αGST, IL-2r, IL-15, sTNFr2 and IL-1ra up to 24 hours before biopsy. No significant increase in IL-6 levels were observed. Compared to these parameters levels of IL-1ra in drainage fluids increased 48 hours before biopsy proven rejection:TableConclusions: Quantification of IL-1ra in peritoneal fluids seems to indicate rejection after liver transplantation 24 hours earlier compared to serum. These findings need to be confirmed by a greater cohort of patients.