Mucosal Ige Antibody Secreting Cell (Asc) Repertoire Analysis Suggests An Extrafollicular Developmental Program

Allergic fungal rhinosinusitis (AFRS) is a subset of chronic rhinosinusitis with nasal polyposis (CRSwNP). AFRS is primarily associated with a type 2 inflammatory profile including eosinophilic mucosal infiltration and high serum and mucosal titers of IgE. Patients with AFRS have increased frequencies of IgE ASCs within NP structures, although it is unclear if these cells originate from a germinal center (GC) reaction or undergo local mucosal extrafollicular differentiation and class switch recombination (CSR). To better understand the origin of these cells, CD19+ and CD19− ASCs from human NPs (n = 3) were isolated for integrated single cell RNAseq and adaptive immune receptor repertoire (AIRRseq) profiling. Resulting AIRRseq data were piped into the ImMunoGeneTics (IMGT) V-Quest platform for comprehensive B cell receptor analysis. Interestingly, mutational frequency analysis showed that IgE ASCs have a lower V region mutation frequency (7.4 +/− 2.7%) compared with IgG (9.2 +/− 3.5%) and IgA (9.4 +/− 3.4%) ASCs from the same individuals. Additionally, IgE ASCs have an intermediate frequency of mutations in activation-induced deaminase WRC hotspots when compared with other isotypes. Finally, IgH repertoire lineage analysis does not indicate clonal expansion of NP IgE ASCs. These data suggest NP IgE ASCs compared to IgG and IgA ASCs from patients with AFRS may undergo a distinct developmental program that includes extrafollicular differentiation and CSR.