title: Immunoglobulin A (IgA) polymerization sites in human immunocytes: immunoelectron microscopic study.
abstract: The cytoplasmic affinity of polymeric IgA for secretory component (SC) and the expression of joining (J) chain were examined in pokeweek mitogen (PWM)-stimulated human peripheral blood lymphocytes (PBL) to determine, on the ultrastructural level, the polymerization sites of human IgA. SC-binding was found in 5.7% of transformed PBL on day 7 of culture; SC-binding was observed in a high proportion of IgA-producing cells. A low proportion of IgM-producing cells also bound to SC, while there was virtually no SC-binding by IgG-producing cells. A high proportion of IgA- and IgM-producing cells expressed intracellular J chain, while approximately half of the IgG-producing cells were positive for J chain. The number of J chain-positive cells exceeded the number of SC-binding cells among transformed PBL on day 7 of culture. Immunoelectron microscopic study of the sites of SC-binding, and of IgA and J chain expression, revealed that polymerization of human IgA and the addition of J chain occur in the perinuclear space and endoplasmic reticulum, prior to immunoglobulin secretion.
authors.affiliation: Department of Pathology, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Moro
authors.forename: T
authors.initials: T
authors.lastname: Iwase
authors.forename: K
authors.initials: K
authors.lastname: Komiyama
authors.forename: Z
authors.initials: Z
authors.lastname: Moldoveanu
authors.forename: J
authors.initials: J
authors.lastname: Mestecky
mesh_terms: D000328:Adult; D001402:B-Lymphocytes / Q000187:drug effects / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000096:biosynthesis*; D007144:Immunoglobulin J-Chains / Q000378:metabolism; D007075:Immunoglobulin M / Q000096:biosynthesis; D008297:Male; D011043:Pokeweed Mitogens / Q000494:pharmacology; D012635:Secretory Component / Q000378:metabolism
chemical_list: D007070:Immunoglobulin A; D007144:Immunoglobulin J-Chains; D007075:Immunoglobulin M; D011043:Pokeweed Mitogens; D012635:Secretory Component; C034639:polymeric IgA; C024242:polymeric IgM