STUDIES ON TRANSLOCATION OF IMMUNOGLOBULINS ACROSS INTESTINAL EPITHELIUM .2. IMMUNOELECTRON-MICROSCOPIC LOCALIZATION OF IMMUNOGLOBULINS AND SECRETORY COMPONENT IN HUMAN INTESTINAL-MUCOSA

Abstract

To define mechanisms involved in the transport of immunoglobulins (Ig) into intestinal fluids, IgM, IgA, IgG and secretory component (SC) were localized in human intestinal mucosa by the peroxidase-labeled antibody technique. At the light microscopic level, immunocytes containing IgA, IgM or IgG were found in the lamina propria. IgA, IgM and SC were prominent in the epithelium of gland crypts; IgG was limited to a few cells at the tips of villi. At the EM level, SC was localized to perinuclear spaces, endoplasmic reticulum, saccules associated with Golgi complexes, cytoplasmic vesicles and lateral and basal plasma membranes of columnar epithelial cells. IgA and IgM, but not IgG, were localized to plasma membranes and cytoplasmic vesicles of these cells. Neither the Ig nor SC was found within other types of epithelial cells (Paneth, goblet and endocrine). The findings provided the following evidence: the site of SC synthesis in intestinal epithelium was secretory columnar cells, principally those in gland crypts; polymeric IgM and IgA were translocated through such SC containing cells by a process that involves formation of cytoplasmic vesicles; IgM and IgA could combine with SC during transcellular transport (likely sites are lateral or basal plasma membranes or supranuclear cytoplasm); monomeric IgG does not share the transepithelial cell route involved in IgM and IgA transport.