When activated, lymphocytes secrete glycoproteins related to particular surface proteins, including soluble forms of the interleukin-2 receptor (sIL-2R) and of the surface proteins CD4 (sCD4) and CD8 (sCD8). We evaluated the release of these glycoproteins in order to assess the activation of the cellular immune system during the course of acute pancreatitis. Thirty-five patients with acute pancreatitis (22 M, 13 F, mean age 64 years, range 16-97) were studied. The diagnosis was based on typical abdominal pain associated with a twofold increase of serum lipase as well as morphological abnormalities compatible with acute pancreatitis seen at computed tomography and/or ultrasonography. The pancreatitis was of biliary origin in 22 patients, due to alcohol abuse in 8, due to pancreas divisum in 1, due to type IV hyperlipoproteinemia in 1 and of unknown origin in 3. Based on clinical outcome, 22 patients had mild pancreatitis, whereas 13 had severe disease. In all patients serum sIL-2R, sCD4 and sCD8 were determined on admission and daily for the following 5 days using enzyme immunoassay (EIA) techniques. Serum concentrations of sIL-2R and sCD8 were significantly higher in acute pancreatitis patients relative to healthy controls during the entire observation period, whereas sCD4 levels were significantly lower in acute pancreatitis patients than in the control group from the 2nd to the 6th day of observation. Serum sIL-2R concentrations were significantly higher in patients with severe pancreatitis than in those with the mild form of the disease, whereas no differences in serum concentrations of sCD8 and sCD4 were found between patients with mild pancreatitis and those with severe disease.(ABSTRACT TRUNCATED AT 250 WORDS)