AIM: To evaluate the cellular synthetic ability of cytokines involved in pro- and anti-inflammatory reactions in patients with AP.METHODS: Sixty-seven patients with AP (16 severe,51 mild) and 10 controls were included in the study.Cultures of whole blood were performed in samples obtained within the first 72 h from the onset of pain.Serum levels of interleukins (IL) 6, 8, 10, and TNF-α were measured at baseline and in the supatant of cultures with (functional reserve) or without stimulation with phytohemaglutinin.RESULTS: Basal levels of cytokines were significantly higher in patients with severe AP. A significant increase of all pro-inflammatory cytokines vs basal levels was observed in the supatant after 24 h of whole blood cultures in patients, but not in controls. In contrast, IL-10 increased significantly in the supatant of cultures only in patients with mild AP. Cells showed a statistically significant functional reserve for all IL in patients with mild, but only for pro-inflammatory cytokines in patients with severe AP.CONCLUSION: A marked activation of immune system may be observed in patients with AP, being balanced between pro- and anti-inflammatory cytokines in patients with mild but not severe AP. A reduced functional reserve for the synthesis of IL-10 may be observed in patients with severe AP, which might lead to a worst prognosis.