Opsonin receptor expression on peritoneal exudative and circulatory neutrophils in murine acute pancreatitis

Acute severe (necrotizing) pancreatitis is often associated with pancreatic or peripancreatic infection. Decreased bacterial clearance due to impaired immune defense may cause local infection. We investigated expressions of s urface opsonin receptors (CD11b, complement receptor 3; CD32/CD16, immunogl obulin G Fc receptor) on local and circulatory neutrophils, in murine acute pancreatitis. The mild and severe forms of acute pancreatitis were induced by seven and 13 subcutaneous injections of caerulein, respectively. Perito neal exudative and circulatory neutrophils were counted and assayed for rec eptor expressions by flow cytometry, serially at 1-72 hours after pancreati tis induction. Histologically, mild and severe forms showed edematous and n ecrotizing pancreatitis, respectively. The peritoneal exudative neutrophil count was greater in mild than in severe pancreatitis. Expressions of CD11b and CD32/CD16 on Local neutrophils were upregulated early in mild pancreat itis. This upregulation was attenuated in severe pancreatitis. The circulat ory neutrophil count was elevated in severe pancreatitis but was unchanged in mild pancreatitis. Opsonin receptor expression on circulatory neutrophil s showed a transient, modest upregulation in the early phase of mild pancre atitis. Receptor-positive circulatory neutrophils showed a marked elevation that persisted throughout the course of severe pancreatitis. In conclusion , severe (necrotizing) pancreatitis is associated with reduced opsonin rece ptor expression on local neutrophils and enhanced expression on circulatory neutrophils, as compared with mild (edematous) pancreatitis. These changes may contribute to local infectious complications and multiple organ failur e, in severe pancreatitis.