Zhai GT, et al. - Researchers focused on the expression and function of soluble IgD in chronic rhinosinusitis (CRS), specifically CRS with nasal polyps (CRSwNP). They used RT-PCR and ELISA to analyze IgD levels in sinonasal mucosa. Immunohistochemistry, immunofluorescence, and flow cytometry were performed to determine the numbers and phenotypes of IgD+ cells. HMC-1 cells and mast cells purified from eosinophilic polyps were culture alone or with naïve B cells purified from peripheral bloods. Using ELISA, the antigen specificity of nasal IgD was determined. CRS patients with or without nasal polyps vs controls exhibited increased mRNA expression of immunoglobulin heavy constant delta gene, the numbers of IgD+ cells, and the protein levels of secretory IgD in sinonasal mucosa. Based on the findings, they concluded that IgD-activated mast cells may facilitate IgE production and eosinophilic inflammation in CRSwNP.