title: Immunohistochemical evaluation of J-chain expression by intra- and extra-follicular immunoglobulin-producing human tonsillar cells.
abstract: Cytoplasmic J-chain expression by Ig-producing cells was characterized immunohistochemically in normal specimens of palatine and nasopharyngeal tonsils (adenoids). Altogether follicular immunocytes, which were mainly of ther IgG and IgM isotypes, showed a much higher percentage of J-chain positivity than the extrafollicular ones, in agreement with the idea that this polypeptide is principally a marker of differentiating or newly differentiated Ig-producing cells. Thus, in concurrence with the predominating IgG isotype, J-chain expression was almost 50% in the germinal centres of lymphoid follicles but only about 2% in the extrafollicular compartment. By contrast, a substantial number of J-chain-positive IgA immunocytes were found in the latter compartment. Since it is believed that extrafollicular Ig-producing cells are mainly derived from follicular centre cells, this result indicated that significant isotype switching is involved in tonsillar B-cell differentiation. Most tonsillar IgD immunocytes were J-chain-positive, in accordance with the notion that IgD expression is a feature of relatively early clonal development. It is postulated that J-chain-positive B-cell blasts may leave the tonsils and, through isotype switching, contribute to the dimer-producing IgA-cell populations normally found in the exocrine glands of the upper aero-digestive tract.
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology; D002454:Cell Differentiation; D002648:Child; D002675:Child, Preschool; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007144:Immunoglobulin J-Chains / Q000032:analysis* / Q000096:biosynthesis; D008297:Male; D014066:Palatine Tonsil / Q000276:immunology*; D010455:Peptides / Q000032:analysis; D013194:Staining and Labeling
chemical_list: D007144:Immunoglobulin J-Chains; D010455:Peptides