Comparison of in vitro binding to enterocyte brush borders of rat IgG subclasses and their transmission in vivo in the rat.

The nature of the Fc receptors for IgG subclasses displayed on the epithelium of the small intestine in neonatal rats was examined by comparing results gained from 125I-IgG binding studies using isolated enterocyte brush borders, and from experiments where in vivo transmission from the gut to the bloodstream was quantified for each subclass. These measurements were made in two strains of rat, Cob Wistar and CB Hooded Nu/+. Subclasses of IgG were transported from gut to blood in different amounts, and the in vitro binding also varied according to isotype. Comparison of the results between rat strains and between isotypes suggested that at least two IgG Fc receptors are present on the enterocytes of the young rat.