Group 2 Innate Lymphoid Cells Directly Induce B Cell Activation in Humans

Abstract

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 virus-induced protein 2 (EBI2). We investigated whether B cells in polyps expressed EBI2, indicating an extrafollicular phenotype, and whether ILC2s could regulate B cell activation. 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. 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). These findings suggest that type 2 inflammation, particularly ILC2s, may play an important role in B cell activation during chronic airway inflammation.