A method for the detection of eosinophilic granulocytes in colonoscopic biopsies from IBD patients

Eosinophilic granulocytes were found to be autofluorescent when Giemsa-stained sections were stimulated with indirect light fluorescence (ILF). The frequency of autofluorescent eosinophils was assessed in areas with diffuse and focal inflammation in 76 consecutive colonoscopic biopsies from patients with inflammatory bowel disease (IBD), Crohn's disease (CD = 32), ulcerative colitis (UC = 30), and collagenous colitis (CC = 7). All IBD cases had moderate to severe pancolitis. In areas with diffuse inflammation, severe eosinophilia was recorded in 39.6% or in 38 of 96 high power fields investigated in patients affected by CD, and in 3.3% or in 3 of 90 high power fields examined in patients with UC. In areas with focal inflammation, the mean percentage of eosinophils in CD was 57% (range 44-70%), and 9% in UC (range 6-26%). No focal inflammation was present in CC. In the submucosa of some CD patients, a large number of autofluorescent eosinophils and many autofluorescent cell-free granules were seen. It was inferred that these autofluorescent granules had been released from eosinophils, and that the eosinophilic granulocytes from which these granules had originated were no longer discernible. Focal eosinophilic mucosal infiltration in CD is more common than epithelioid cell granulomas, and emerges as an important parameter in the histologic differential diagnosis between colonic CD and UC.