Pentraxin 3 (PTX3) is the first identified long pentraxin, and it is rapidly produced and released by several cell types in response to proinflammatory signals. The aim of this study was to investigate the behavior of neutrophils to produce PTX3 protein in response to proinflammatory cytokine IL‐8 in vitro, as well as identify the expression pattern of PTX3 in human ulcerative colitis lesions.

Pentraxin 3 protein was found to be present following release upon IL‐8 stimulation in cultured neutrophils together with lactoferrin⁺‐specific granules localized in neutrophil extracellular traps (NETs) formed by extruded DNA. Neutrophils in colonic mucosal tissue of patients with ulcerative colitis were the main cellular source of PTX3 protein, the expression of which is correlated well with the histological grades of inflammation. Immunofluorescence analysis against anti‐lactoferrin antibody revealed the formation of NETs released from neutrophils within crypt abscess lesions, which were found to be activated through the expression of IL‐8 receptor B (CXCR2). Of interest, neutrophils depleted of PTX3 protein were displayed, supporting the release of PTX3 from neutrophils in crypt abscess. We suspected that PTX3 protein may contribute to cell‐mediated immune defense in inflamed colon tissue, and in particular in crypt abscess lesions, of patients with ulcerative colitis.