Immunohistochemical Characterization of the Pancreatic Cellular Infiltrate in Normal Pancreas, Chronic Pancreatitis and Pancreatic Carcinoma

Background/Aims: Chronic pancreatitis is histologically characterized by an extended fibrosis and infiltration of leukocytes. We intended to differentiate the infiltration to evaluate the inflammatory process. Methods: Samples of tissues of normal pancreas (NP, n = 12), of chronic pancreatitis (CP, n = 7), and pancreatic tissues surrounding pancreatic carcinoma (CA, n = 7) were investigated by immunohistochemical staining using the APAAP technique. Results: In normal pancreas, mononuclear cells (47.1 ± 26.0 cells/mm 2 ) were observed with a predominance of macrophages (56.3%) and T lymphocytes (31.3%) which were differentiated in CD8+ lymphocytes (9.3 ± 7.2 cells/mm 2 ) and CD4+ lymphocytes (6.7 ± 3.2 cells/mm 2 ). Rarely, plasma cells (5.3%) and B lymphocytes (7.1%) could be detected. In pancreatic tissue of patients with CP and in CA there was a significant increase of mononuclear cells to 264.4 ± 120.3 cells/mm 2 and 284.3 ± 67.8 cells/mm 2 , respectively. In both diseases percentages of T lymphocytes (CP: 50.5%; CA: 48.1%) were higher than in normal controls. CD4+/CD8+ ratio of 0.77 in CP and 0.82 in CA demonstrated a predominance of CD8+ cells compared to the peripheral blood. In NP and CA, nearly all T lymphocytes expressed CD45R0 identifying memory cells, while only 58% of T lymphocytes were CD45R0 positive in CP. Conclusion: Our data suggest that the investigated cases of CP were of a common inflammatory type rather than due to an autoimmunological reaction. CD8+ T lymphocytes were the predominant T cell subset in the inflammatory infiltrates in both CP and CA.