Immunohistochemical demonstration of the calcium-binding proteins MRP8 and MRP14 and their heterodimer (27E10 antigen) in Crohn's disease.

Monospecific antibodies against the calcium-binding proteins MRP8 and MRP14 and their heterodimer MRP8/14 (epitope 27E10) were used to investigate immunohistochemically the distribution of these proteins in routinely processed small and large bowel tissues from patients with Crohn's disease. MRP8, MRP14, and complex MRP8/14 were demonstrated in most granulocytes and macrophages in active Crohn's disease. Additionally, a strong complex MRP8/14 immunoreactivity was present in epithelial cells of the terminal ileum adjacent to ulcerative and fissuring lesions, whereas epithelial cells in large bowel tissues were consistently negative. Our results morphologically confirm the clinical finding of increased MRP8/14 serum levels in patients with active Crohn's disease; there is evidence that the serum MRP8/14 increase is caused by active secretion from granulocytes, monocytes, and epithelial cells.