Mucosal IgE antibody secreting cell (ASC) repertoire analysis suggests an extrafollicular developmental program

Abstract

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.

Chronic rhinosinusitis with nasal polyps: eosinophils versus B lymphocytes in disease pathogenesis

“…IgE targeting nasal pathogens such as Staph. aureus [27], autoantigens [28 ▪ ,29,30,31] fungal antigens [32 ▪▪ ] as well as allergens more typically associated with allergic disease [33,34 ▪ ] have all been identified. While this suggests that there may be different antigenic triggers of IgE responses at the individual level, it confirms that the dysregulation of B cell responses results in the local production of antigen-specific antibodies that drives the pathogenesis of CRSwNP through Fc-dependent effector mechanisms.…”

“…Naïve B cells comprise the most abundant B cell subset in peripheral blood, whereas in NP there are relatively higher proportions of plasmablasts and memory B cells (both switched and unswitched). A recent study [32 ▪▪ ] reported that the majority of antibody secreting cells in NP have a double negative phenotype (IgD − CD27 − ), which are typical of extrafollicular responses. Consistent with this, a previous study [36 ▪▪ ] found that NP plasmablasts express high levels of EBI2, a marker associated with extrafollicular B cell responses.…”

The origins and longevity of IgE responses as indicated by serological and cellular studies in mice and humans

“…IgE + ASC have been identified in several tissues by flow cytometry, most notably, in peripheral blood and in nasal polyps, which is associated with local IgE production and detection of target antigens in the tissue 38,128,186–188 . Transcriptomically validated IgE + ASC have been detected in peripheral blood of individuals with atopic diseases, 38,39 in dissected polyps from individuals with allergic rhinitis with nasal polyps, and intestinal mucosa of peanut allergic individuals 127,189–191 (Figure 6). Transcriptome analysis of IgE + ASC suggest that the bulk resolvable IgE + ASC are plasmablasts or immature ASC, rather than mature plasma cells, as they maintain expression of MHC‐II, a marker that is down‐modulated in the first few days after ASC obtain quiescence 38,125,191 .…”

“…Transcriptomically validated IgE + ASC have been detected in peripheral blood of individuals with atopic diseases, 38,39 in dissected polyps from individuals with allergic rhinitis with nasal polyps, and intestinal mucosa of peanut allergic individuals 127,189–191 (Figure 6). Transcriptome analysis of IgE + ASC suggest that the bulk resolvable IgE + ASC are plasmablasts or immature ASC, rather than mature plasma cells, as they maintain expression of MHC‐II, a marker that is down‐modulated in the first few days after ASC obtain quiescence 38,125,191 . Interestingly, one study showed that IgE + ASC lost expression of MKI67 , a marker of the proliferative plasmablast state, suggesting that IgE + ASC can become quiescent 191 .…”

“…Transcriptome analysis of IgE + ASC suggest that the bulk resolvable IgE + ASC are plasmablasts or immature ASC, rather than mature plasma cells, as they maintain expression of MHC‐II, a marker that is down‐modulated in the first few days after ASC obtain quiescence 38,125,191 . Interestingly, one study showed that IgE + ASC lost expression of MKI67 , a marker of the proliferative plasmablast state, suggesting that IgE + ASC can become quiescent 191 . Thus, while transcriptomic evidence has confirmed that immature IgE + ASC exist, we await transcriptomic depictions of mature IgE + ASC or bone marrow IgE + ASC with potential for longevity (Figure 6).…”