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Tests in patients with colorectal disease have confirmed that lipocalin—a protein released from neutrophils—is a specific marker for monitoring neutrophil activity in the inflammatory process. Demonstrating the secretion and specificity of human neutrophil lipocalin (HNL) in vivo confirms the researchers' previous work on isolation of HNL from the secondary granules of neutrophils and makes HNL ideal for studying neutrophil behaviour in the local inflammatory process characteristic of ulcerative colitis.

Perfusion tests showed much higher amounts of HNL in the perfusion fluid from rectal and sigmoid segments of the intestine in patients with proctitis (median concentration 245 μg/ml (upper-lower quartile 149–557 μg/ml; 13.4 μg/ml (7.8–21.4 μg/ml) respectively) and colitis (358 μg /ml (55.2–430 μg /ml); 105 μg/ml (19.6–586 μg /ml) respectively) than tests in healthy controls (rectal 9.2 μg/ml (3.3–13.2 μg /ml); sigmoid (<2 μg/ml)). HNL was shown histochemically in mucosal specimens from these patients to be confined exclusively to neutrophils—in the lamina propria, between crypt cells, and in the lumen of crypts in inflamed areas of the rectal and sigmoid intestine. The amount of HNL in the perfusion fluid correlated significantly with clinical scores for disease for rectal segments in patients with proctitis and both rectal and sigmoidal segments for colitis.

Eighteen patients—10 with colitis and eight with proctitis—and 18 healthy controls were perfused in the sigmoid and rectal segments of their intestine. HNL released into the fluid was subsequently measured by radioimmunoassay. Mucosal tissue from the perfused segments was obtained by biopsy in all subjects, and thin sections were stained immunohistochemically with a mixture of six monoclonal antibodies specific for HNL.