Ileal Mucosal Mast Cell, Eosinophil, and Goblet Cell Populations During Hymenolepis diminuta Infection of the Rat

The population dynamics in the enteric connective tissues of eosinophils, mucosal mast cells (MMC), and in the mucosal epithelium of goblet cells were examined morphometrically in fixed ileal tissue of outbred Sprague Dawley rats during the first 32 days of infection with the tapeworm Hymenolepis diminuta. MMC and eosinophils were present in the lamina propria and submucosa; however, only eosinophils were also present in the muscularis externa. Eosinophilic infiltrate was first observed in the lamina propria at 15 days postinfection (dpi) and the numbers of eosinophils remained elevated through 32 dpi. Initial mucosal mastocytosis was detected on 6 dpi and MMC numbers continued to rise over the study period without reaching a plateau. Goblet cell hyperplasia occurred only at 32 dpi. In contrast to some intestinal nematode infections where these same 3 cell types are associated with the host's expulsion responses, H. diminuta is not lost by a rapid host response in the outbred Sprague Dawley rat strain used in these experiments. We suggest that either the induction of hyperplasia of these host effector cells in ileum tissue during H. diminuta infection is not capable of triggering parasite rejection mechanisms, or the function of the induced hyperplasia is necessary for some as yet unassociated physiological or tissue architecture change in the host's intestine.