Histological enzyme and flow cytometric analysis of channel catfish intestinal tract immune cells

Channel catfish, Ictalurus punctatus, gastrointestinal tract leukocytes wer e characterized using flow cytometry, histochemistry, and enzyme staining t echniques. Cells obtained from the lamina propria by collagenase digestion were found to be primarily neutrophils, with fewer than 6% B lymphocytes as determined by flow cytometry. Histochemical and enzyme stains were used to determine leukocyte distribution in gastrointestinal tract tissue. Macroph ages and T lymphocytes were observed throughout the gastrointestinal tract. As in flow cytometry studies, few B lymphocytes and many neutrophils were observed in the channel catfish gastrointestinal tract. Since cells involve d in specific immunity appear to be limited in gastrointestinal tract tissu e of channel catfish, we speculate that catfish may rely more heavily on a highly developed innate response for intestinal mucosal immunity than other teleost species studied. (C) 2001 Elsevier Science Ltd. All rights reserve d.