Nature Communications | Spatial and Functional Specialization of Human Splenic Innate Lymphoid Cells

This study elucidates the mechanism by which specific innate lymphoid cell (ILC) subsets in the spleen regulate B cell survival and antibody class switching via CD40L and BAFF, providing critical target validation strategies for developing immunotherapies targeting humoral immune dysregulation or autoimmune diseases.

 

Literature Overview

This article, "Spatial and functional specialization of human splenic innate lymphoid cells," published in Nature Communications, systematically explores the spatial distribution, phenotypic heterogeneity, and functional networks of Natural Killer (NK) cells and various innate lymphoid cells (ILCs) in the human spleen. By integrating CITE-seq with spatial transcriptomics, the study maps a high-resolution human splenic ILC atlas for the first time, clarifying the specific regulatory roles of different subsets in B cell germinal center reactions and antibody production.

Background Knowledge

As a secondary lymphoid organ, the spleen is a critical site for integrating innate and adaptive immune responses; however, the in situ organization and interaction networks of innate lymphoid cells within it remain incompletely understood. This research aims to address the gap in understanding B cell regulatory mechanisms in autoimmune diseases and humoral immunodeficiencies. Currently, there are bottlenecks in understanding the specific functional differentiation of NK cells and ILC3s within the splenic microenvironment, particularly how they synergistically regulate B cell proliferation, differentiation, and IgA or IgG class switching. The study leverages spatially resolved technologies to distinguish the unique functions of CD56bright NK cells, ILC2s, and three ILC3 subsets (KLF2+, CD38+, IFNGR1+) across different splenic regions (e.g., red pulp vs. white pulp), thereby filling the knowledge gap from tissue localization to immunoregulatory function.

 

 

Research Methods and Experiments

The authors utilized CITE-seq technology to deeply sequence seven normal human spleen samples and three peripheral blood mononuclear cell (PBMC) samples, combining this with the Xenium spatial transcriptomics platform to resolve cellular spatial localization and interaction relationships in situ. The study first validated the heterogeneity of splenic NK cells via flow cytometry, specifically identifying unique tissue-resident characteristics of CD56bright NK cells in the spleen. Subsequently, co-culture experiments were conducted by incubating isolated splenic ILC2s or ILC3s with autologous B cells to assess their impact on B cell proliferation and antibody secretion. Key evidence revealed that spatial analysis showed the spatial proximity of CD56bright NK cells to CD163+ macrophages, while ILC2s were enriched in perivascular regions and highly expressed CD40L.

Key Conclusions and Perspectives

• It was discovered that splenic CD56bright NK cells highly express CD39 and TIGIT, localize outside B cell follicles, and interact with alternatively activated macrophages, suggesting immunosuppressive or regulatory functions. This provides guidance for future research on the "braking" mechanisms of NK cells in germinal center reactions.
• A splenic ILC2 subset was identified that highly expresses CD40L, significantly promoting B cell proliferation and inducing the secretion of IgA, IgG3, and IgD in co-culture. This indicates that ILC2s can drive humoral immunity even in non-mucosal environments, offering a new perspective on B cell activation mechanisms.
• Three spatially and functionally distinct ILC3 subsets were defined: KLF2+ progenitor-like ILC3s enriched in the red pulp interacting with CD8+ T cells; CD38+ ILC3s located in B cell follicles, highly expressing BAFF and HLA-DR to support plasmablast maturation; and IFNGR1+ ILC3s that promote B cell survival and IgG class switching while inducing IL-10 production. These findings provide specific targets for targeting ILC3s to regulate antibody responses.

Research Significance and Prospects

These findings have profound implications for antibody drug development and autoimmune disease treatment, particularly by clarifying the critical roles of CD38+ ILC3s and ILC2s in regulating B cell class switching. This suggests that pathological antibody production could be modulated by intervening in the CD40L-CD40 or BAFF pathways. Furthermore, this atlas provides new cellular targets for disease modeling, facilitating more precise simulation of the human splenic immune microenvironment in gene-edited animal models to evaluate the efficacy of new drugs targeting humoral immune dysregulation.

 

 

Conclusion

Through multi-omics integrative analysis, this study constructed a high-resolution spatial and functional atlas of human splenic innate lymphoid cells. It not only revealed the fine division of labor among NK cells and ILC subsets within the splenic microenvironment but also elucidated the molecular mechanisms by which they act as key regulators of B cell fate. From laboratory discovery to clinical translation, this achievement provides a new theoretical foundation for understanding autoimmune diseases, lymphoma, and vaccine responses. Specifically, the regulatory roles of CD38+ ILC3s and ILC2s in B cell survival and antibody class switching suggest potential intervention targets, offering the prospect of guiding the development of novel therapeutic strategies for humoral immune abnormalities, thereby optimizing the care system for patients with immune-related diseases.

 

Sarah J Colpitts, Sinthuja Jegatheeswaran, Siavash Mashhouri, Clinton S Robbins, and Sarah Q Crome. Spatial and functional specialization of human splenic innate lymphoid cells. Nature Communications.