Secretory Component in Immunoglobulin Deficiency: an Immunoelectron Microscopic Study of Intestinal Epithelium

Abstract

The ultrastructural sites of secretory component (SC) in the intestinal epithelium of severely Ig-deficient and immunologically intact persons were compared. SC was found in the same sites in the Ig-deficient and normal epithelium which are as follows: perinuclear spaces, rough endoplasmic reticulum, Golgi complexes, external surfaces and endocytic invaginations of the basolateral plasmalemma and in membranous vesicles throughout the cytoplasm. The synthesis, external expression and transcellular migration of SC probably occur independent of the presence of Ig. The migration of SC from the basolateral cell surfaces to apical surfaces may be an inherent property of epithelial cells and the primary event in the translocation of polymeric Ig across the cells to external body fluids.