Occurrence and IgE binding of mucosal mast cells in neonates

Abstract

Maternal IgE is exclusively transferred to the neonatal foal via colostrum after birth. The primary contact site for maternal IgE is the foal's gut tissue. Our goal was to investigate neonatal tissues for the presence of mucosal mast cells (MCs), and to test whether intestinal neonatal MCs can bind maternal IgE. Tissues from the small intestine, mesenteric and peripheral lymph nodes were harvested immediately after birth (before colostrum uptake), and on days 5, 9 and 36 from healthy neonates. Mucosal MCs were detected using Alcian blue staining. At birth, most MCs were found in the crypt areas of the small intestine. On days 5 and 9, only a few mucosal MCs could be detected. On day 36, many MCs were found in the submucosa. Mucosal MCs were observed in the T‐cell areas of lymph nodes at all time points. To investigate whether intestinal MCs can bind maternal IgE directly after birth, MCs were isolated from the mucosa of the jejunum. The cells were cultured in the presence of fluorochrome conjugated IgE and measured by flow cytometry. Two populations of IgE+ cells were detected. First, an IgEhigh+/MHC class II− population; and second, cells of a IgE+/MHC class II+ phenotype. We concluded that intestinal mucosal MCs express IgE receptors to rapidly bind maternal IgE from ingested colostrum.