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

Marginal zone B cells provide rapid antibody responses to blood-borne antigens. Cerutti and colleagues identify a RORγt-dependent innate lymphoid cell subset that establishes crosstalk among multiple cell types to enhance antibody responses. Innate lymphoid cells (ILCs) regulate stromal cells, epithelial cells and cells of the immune system, but their effect on B cells remains unclear. Here we identified RORγt + ILCs near the marginal zone (MZ), a splenic compartment that contains innate-like B cells highly responsive to circulating T cell–independent (TI) antigens. Splenic ILCs established bidirectional crosstalk with MAdCAM-1 + marginal reticular cells by providing tumor-necrosis factor (TNF) and lymphotoxin, and they stimulated MZ B cells via B cell–activation factor (BAFF), the ligand of the costimulatory receptor CD40 (CD40L) and the Notch ligand Delta-like 1 (DLL1). Splenic ILCs further helped MZ B cells and their plasma-cell progeny by coopting neutrophils through release of the cytokine GM-CSF. Consequently, depletion of ILCs 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 system and circulatory system.