Regulation of immunoglobulin secretion by plasma cells infiltrating nasal polyps

Objective/Hypothesis: To learn more about the role of plasma cells infiltra ting nasal polyps in the pathogenesis of nasal polyposis, we examined their function by analyzing immunoglobulin (Ig) production and the factors impli cated in the secretion. Study Design A series of 19 consecutive nasal polyp tissue samples and, as a control, peripheral blood samples from the same p atients, were studied by histopathological and immunological examination, M ethods: 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-secre ting cells were identified in cytospin preparations stained with fluorescei n isothiocyanate-conjugated antibodies against IgA, IgG, IgM and IgE, Purif ied NPMNCs were cultured in basal conditions and after the addition of seve ral stimuli. Ig secreted into the culture supernatants was evaluated by an enzyme-linked immunosorbent assay. Results: Plasma cells accounted for an i mportant fraction of the inflammatory infiltrate, The main Ig isotype synth esized by these cells was IgA, whereas little IgE was detected. In vitro cu ltures demonstrated that the plasma cells actively secreted Ig for a short period. When cytokine dependence was analyzed, interleukin-10 (IL-10) and t umor necrosis factor-alpha (TNF-alpha) were shown to be partially responsib le for the Ig production. Dependence on CD95-mediated apoptosis was not obs erved. Conclusions: Nasal polyp-infiltrating plasma cells are mainly IgA-se creting cells, the latter property being related to the mucosal immune syst em. The IgA production is partly dependent on IL-10 and TNF-alpha. The abse nce of IgE-secreting cells in most of the samples suggests that a type I hy persensitivity reaction is not essential for the development of nasal polyp .