Background B cells play many roles in health and disease. However, little is known about the mechanisms that drive B cell responses in the airways, especially in humans. Chronic rhinosinusitis (CRS) is an inflammatory disease of the upper airways that affects 10% of Europeans and Americans. A subset of CRS patients develop nasal polyps (NP), which are characterized by type 2 inflammation, eosinophils and group 2 innate lymphoid cells (ILC2). We have reported that NP contain elevated levels of B cells and antibodies, making NP an ideal system for studying B cells in the airways. Objective We sought to determine the mechanisms that drive B cell activation and antibody production during chronic airway inflammation. Methods We analyzed B cells from NP or tonsil, or after ILC2 co-culture, by flow cytometry. Antibody production from tissue was measured using Luminex assays, and the frequency of antibody-secreting cells by ELISpot. Formation of B cell clusters was assessed using immunohistochemistry. Expression of genes associated with B cell activation and class switch recombination was measured by qRT-PCR. Results NP contained significantly elevated frequencies of plasmablasts, especially those that expressed the extra follicular marker Epstein-Barr virus-induced protein 2 (EBI2), but significantly fewer germinal center (GC) B cells compared to tonsil. Antibody production and the frequency of antibody-secreting cells were significantly elevated in NP, and there was evidence for local class switch recombination in NP. Finally, ILC2s directly induced EBI2 expression on B cells in vitro. Conclusions and Clinical Relevance Our data suggest there is a unique B cell activation environment within NP that is distinct from classic GC-mediated mechanisms. We show for the first time that ILC2s directly induce EBI2 expression on B cells, indicating that ILC2s may play an important role in B cell responses. B cell-targeted therapies may provide new treatment options for CRSwNP.

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These in vitro observations indicate that testis epididymal secretions contain androgen/STEP synergistic and androgen independent STEP factors promoting prostate stromal growth. These factors are not heparin binding. These observations are consistent with the concept that, in addition to the production of steroids, the testis produces non-androgenic factors that act in concert with, as well as independently of, androgen to stimulate prostatic growth.

The observations presented provide evidence for human testis/epididymis secretion of PEDF and for a PEDF in vitro growth promoting effect on benign prostatic hyperplasia stroma. The concept that testicular epididymal secretory proteins may influence normal and abnormal prostate growth warrants continued consideration.

RATIONALE: Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by type 2 inflammation and increased group 2 innate lymphoid cells (ILC2). We have also found elevated B cells and overexpression of the extrafollicular B cell marker Epstein-Barr virusinduced protein 2 (EBI2). We investigated whether B cells in polyps expressed EBI2, indicating an extrafollicular phenotype, and whether ILC2s could regulate B cell activation. METHODS: EBI2 expression on cells from polyps of CRSwNP patients or tonsils from non-CRS patients was assessed by flow cytometry. Antibody production by tissue B cells was assessed by Luminex assay. In other experiments, B cells and ILC2s were isolated from peripheral blood by magnetic bead-and flow cytometry-based methods, respectively. B cells were cultured for 5 days under IgG-promoting conditions (IL-2 and R848 (a TLR7/8 agonist)), or IgE-promoting conditions (IL-4 and anti-CD40), or with autologous ILC2s at a 1:1 ratio, or with IL-2 alone. RESULTS: Polyps contained elevated levels of plasmablasts (PB) and EBI2 + PB compared to tonsil (>5 fold, p<0.001 and >2.5 fold, p<0.01, respectively). In vitro, polyps also produced significantly higher levels of antibodies (p<0.01). IL-4 and anti-CD40 increased B cell survival and EBI2 expression (>5 fold), indicating in vitro development of extrafollicular PB, while IL-2 and R848 had no effect on EBI2. Co-culture of B cells with ILC2s increased B cell survival and promoted a significant increase of EBI2 + B cells (>5 fold, p<0.05). CONCLUSIONS: These findings suggest that type 2 inflammation, particularly ILC2s, may play an important role in B cell activation during chronic airway inflammation.