Eosinophil Infiltration and Degranulation in Normal Human Tissues: Evidence for Eosinophil Degranulation in Normal Gastrointestinal Tract

Eosinophils play an important role in the pathogenesis of inflammatory diseases such as bronchial asthma and host immunity to parasitic infections. Deposition of eosinophil granule proteins and concomitant tissue damage have been documented in various diseases. Here, we review and summarize results of our immunofluorescence studies of eosinophil infiltration and degranulation in various normal human tissues. Furthermore, because eosinophil infiltration and degranulation are not normally present in healthy tissues, we examine whether eosinophil infiltration and degranulation normally occur in the small intestine and whether tissue procurement methods affect the extent of eosinophil infiltration and degranulation there. Hematopoietic and lymphatic tissues, including the thymus, showed eosinophil infiltration, but the only organ showing remarkable eosinophil infiltration and degranulation was the gastrointestinal (GI) tract. Eosinophil degranulation was significantly increased in specimens obtained by endoscopic forceps compared to those obtained by scalpel. These results suggest that tissue procurement methods affect the degree of eosinophil degranulation in the GI tract and that, among normal human body organs, both eosinophil infiltration and degranulation only occur in the GI tract.