Ultrastructural Localization of J Chain in Human Intestinal Mucosa

Abstract

J chains were localized by immunoperoxidase cytochemistry in the intestinal mucosa of immunologically intact patients and of patients with immunoglobulin deficiency and associated intestinal nodular lymphoid hyperplasia. J chains were present in an aggregate of lymphocytes from one of two immunologically intact patients and in lymphoid nodules from two of five immunodeficient patients. Ultrastructurally, the J chains were localized to the perinuclear spaces and endoplasmic reticulum of the lymphocytes, but not to the plasma membranes. A few of the J chain-containing cells resembled activated lymphocytes, but most corresponded to less mature cells with IgM expressed on their surface membranes. J chains were present also in numerous plasma cells in the lamina propria of the immunologically intact patients and in a few plasma cells in the immunodeficient patients. The J chains in plasma cells were localized to the perinuclear spaces and endoplasmic reticulum, and infrequently to elements of the Golgi apparatus. Acid-urea treatment of the plasma cells intensified the reactions for J chains in the endoplasmic reticulum, but did not reveal additional evidence of J chains in Golgi organelles. J chains were not seen in columnar epithelial cells before acid-urea treatment, but afterward, J chains as well as IgA, IgM, and secretory component were found on basolateral plasma membranes and in intracellular vesicles.The findings indicate that: 1) J chains in B lymphocytes may appear before distinct morphologic evidence of blast transformation; 2) J chains may combine with immunoglobulin polymers in the endoplasmic reticulum of lymphoid cells; 3) J chain-containing immunoglobulin polymers probably are continually in complex with secretory component, their membrane-bound receptor, during transit across intestinal epithelial cells.