Innate lymphoid cells integrate stromal and immunological signals to enhance antibody production by splenic marginal zone B cells

Abstract

Innate lymphoid cells (ILCs) regulate stromal, epithelial and immune cells, but their impact on B cells remains unclear. We identified RORγt+ ILCs nearby the marginal zone (MZ), a splenic compartment containing innate-like B cells that respond to circulating T cell-independent (TI) antigens. Spenic ILCs established a bidirectional crosstalk with MAdCAM-1+ marginal reticular cells by providing tumor necrosis factor (TNF) and lymphotoxin, and activated MZ B cells via BAFF, CD40 ligand and the Notch ligand, Delta-like 1. Splenic ILCs further helped MZ B cells and their plasma cell progeny by co-opting neutrophils through the release of GM-CSF. Consequently, ILC depletion impaired both pre- and post-immune TI antibody responses. Thus, ILCs integrate stromal and myeloid signals to orchestrate innate-like antibody production at the interface between the immune and circulatory systems.

CD 1d‐mediated activation of group 3 innate lymphoid cells drives IL ‐22 production

“…Consequently, engagement of epithelial CD1d renders protective effects in mouse models of IBD, while CD1d‐mediated production of IL‐12 by APCs leads to protection against viral infection 14, 23. To study whether CD1d could regulate ILC3 function, we performed antibody‐mediated cross‐linking of CD1d on ILC3s and measured changes in the expression of IL22 , IL17A, LTA and LTB (cytokines typically produced by ILC3s) as well as TNFSF13B (BAFF), TNFSF1 3 (APRIL) and CD40LG (CD40L; factors by which ILC3s modulate B‐cell function 28; Figs 3C and EV5). Strikingly, CD1d ligation on ILC3s resulted in a prominent increase in the expression of IL22 mRNA (Fig 3C and D), suggesting that CD1d engagement is sufficient to induce cytokine production by ILC3s.…”

“…Splenic ILC3s were enriched by using lineage cell depletion kit (Miltenyi Biotec). ILC3s were further purified by cell sorting as CD45 + CD127 + CD117 + B220 − CD3 − CD5 − CD11c − CD11b − cells 3, 9, 28 with a FACSAria II (BD Biosciences). Sorted ILC3s were cultured in complete RPMI medium supplemented with 10% FCS.…”

“…Sorted ILC3s were cultured in complete RPMI medium supplemented with 10% FCS. For cross‐linking experiments, ILCs were expanded for 5–8 days with IL‐7 (50 ng/ml) and IL‐2 (100 ng/ml) as described 28, 47.…”

Functional and phenotypic heterogeneity of group 3 innate lymphoid cells

“…LTi‐like ILC3 express both membrane‐bound lymphotoxin heterotrimers (LT α 1 β 2 ) as well as soluble lymphotoxin α homotrimers (LT α 3 ), which control T‐independent and T‐dependent IgA responses, respectively 105, 106. Human and mouse splenic ILC3 also stimulate innate‐like B‐cell IgG production through CD40 interactions, production of BAFF/APRIL and via the Notch ligand Delta‐like 1 108, 109. Taken together ILC3 demonstrate increasingly expanding roles in modulating adaptive immune responses.…”

Immunoglobulin gene analysis as a tool for investigating human immune responses

“…Signaling via Toll Like receptors (TLRs) can complement signaling through the BCR to activate both the non‐canonical and canonical NFkB pathways and initiate class switching 43. Similarly, binding of APRIL or BAFF, produced by accessory cells such as neutrophils,44 innate lymphoid cells45 or fibroblasts,46, 47 to TACI on the B cell surface will activate the NFkB pathway via MyD88 to cause expression of AID and class switching 48. Expression of AID can also be increased by estrogen acting via the HoxC4 AICDA gene activator 49…”