Regulation of immunoglobulin secretion by plasma cells infiltrating nasal polyps

To learn more about the role of plasma cells infiltrating nasal polyps in the pathogenesis of nasal polyposis, we examined their function by analyzing immunoglobulin (Ig) production and the factors implicated in the secretion.

A series of 19 consecutive nasal polyp tissue samples and, as a control, peripheral blood samples from the same patients, were studied by histopathological and immunological examination.

Hematoxylin-eosin and immunohistochemical staining was carried out to identify plasma cells infiltrating nasal polyps. Nasal polyp mononuclear cells (NPMNCs) were purified from nasal polyp tissue samples, and Ig-secreting cells were identified in cytospin preparations stained with fluorescein isothiocyanate-conjugated antibodies against IgA, IgG, IgM, and IgE. Purified NPMNCs were cultured in basal conditions and after the addition of several stimuli. Ig secreted into the culture supernatants was evaluated by an enzyme-linked immunosorbent assay.

Plasma cells accounted for an important fraction of the inflammatory infiltrate. The main Ig isotype synthesized by these cells was IgA, whereas little IgE was detected. In vitro cultures demonstrated that the plasma cells actively secreted Ig for a short period. When cytokine dependence was analyzed, interleukin-10 (IL-10) and tumor necrosis factor-alpha (TNF-alpha) were shown to be partially responsible for the Ig production. Dependence on CD95-mediated apoptosis was not observed.

Nasal polyp-infiltrating plasma cells are mainly IgA-secreting cells, the latter property being related to the mucosal immune system. The IgA production is partly dependent on IL-10 and TNF-alpha. The absence of IgE-secreting cells in most of the samples suggests that a type I hypersensitivity reaction is not essential for the development of nasal polyp.