Expression of immunoglobulin D is increased in chronic rhinosinusitis

Background: Immunoglobulin (Ig) D is largely localized to the upper airway and reacts with colonizing respiratory pathogens. Objective: To determine whether chronic rhinosinusitis (CRS) is associated with increased IgD expression. Methods: We performed immunofluorescent staining for cytoplasmic IgD, IgA, IgM, and surface plasma cell marker CD138 (syndecan-1) in sinus tissue of patients with CRS with and without nasal polyps (CRSwNP and CRSsNP, respectively) and control subjects without CRS (n = 6 each). Sinonasal mucus antibody levels of patients with CRSwNP or CRSsNP and control subjects were measured by enzyme-linked immunosorbent assay (n = 13, 11, and 9 subjects, respectively). Cells per square millimeter and antibody levels were compared by analysis of variance. Histopathology was performed with sinus tissue from subjects in the 3 groups (n = 6, 8, and 13 subjects respectively). Results: Cells expressing cytoplasmic IgD exceeded those with cytoplasmic IgA and IgM and represented most CD138(+) plasma cells in the lamina propria. The frequencies of IgD(+) plasma cells were significantly higher in patients with CRSsNP and CRSwNP compared with control subjects (P < .01). Only patients with CRSwNP showed increased frequencies of IgM and IgA plasma cells (P < .01). In contrast to high plasma cell frequencies in tissues, the levels of secreted IgD were lower than those of IgA, IgM, and IgG but were highest in the CRSwNP group compared with the other groups (P < .05). Conclusion: IgD plasma cells are prominent in sinus tissues and are increased in CRS. That IgD protein also shows the lowest concentration of antibodies in secretions suggests that its activity might be targeted to the tissue rather than secretions. (C) 2017 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.