Evidence for the Presence of Long-Lived Plasma Cells in Nasal Polyps

Plasma cells and immunoglobulins (Igs) play a pivotal role in the induction and maintenance of chronic inflammation in nasal polyps. During secondary immune responses, plasma cell survival and Ig production are regulated by the local environment. The purpose of the present study was to investigate the presence of long-lived plasma cells (LLPCs) and specific survival niches for LLPCs in human nasal polyps.

Nasal mucosal samples were cultured with an air-liquid interface system and the Ig levels in culture supernatants were analyzed by enzyme-linked immunosorbent assay. The characteristics of LLPCs in nasal polyps were determined by immunohistochemistry and immunofluorescence. The expression of neurotrophins as well as their receptors was detected by quantitative real-time polymerase chain reaction, immunohistochemistry, immunofluorescence, and Western blotting.

The numbers of CD138⁺ total plasma cells and BCL2⁺ plasma cells were increased in both eosinophilic and non-eosinophilic nasal polyps compared with those in normal tissues. The production of IgG, IgA, and IgE was detected in culture supernatants even after a 32-day culture of nasal polyps. Although the total numbers of plasma cells were decreased in nasal polyps after culture, the numbers of BCL2⁺ plasma cells remained stable. The expression of nerve growth factor (NGF) as well as tropomyosin receptor kinase (Trk) A, a high-affinity receptor for NGF, was upregulated in both eosinophilic and non-eosinophilic nasal polyps. In addition, BCL2⁺ plasma cell numbers were positively correlated with NGF and TrkA mRNA expression in nasal mucosal tissues. Polyp plasma cells had the expression of TrkA.

Human nasal polyps harbor a population of LLPCs and NGF may be involved in their prolonged survival. LLPCs may be a novel therapeutic target for suppressing the local Ig production in nasal polyps.