Innate lymphoid cells (ILCs) are found in the spleen, where they promote antibody production by marginal zone B cells, according to a recent study in Nature Immunology (15, 354–364, 2014) .

ILCs are commonly found at barrier surfaces where, in response to environmental stimuli, they provide an important source of cytokines that prime the development and function of immune cells. Although ILCs have been shown to support antibody production at mucosal surfaces, whether these cells also function in the spleen is not clear.

Andrea Cerutti and his colleagues now report that in humans, ILCs are found within the marginal zone of the spleen and exhibit a phenotype similar to mucosal ILCs. These ILCs interact with and receive survival signals from stromal cells within the spleen that help promote their function. ILCs are positioned near B cells and promote the survival and differentiation of marginal zone B cells and plasma cells via B cell–activating factor (BAFF), CD40 ligand and the Notch ligand delta-like ligand 1 (DLL1). In addition, ILCs help recruit neutrophils to the spleen, which, in turn, promotes antibody production. In the absence of splenic ILCs, T cell–independent antigen antibody production is impaired. These findings suggest ILCs provide crosstalk between stromal cells and different arms of the immune system to support antibody production.