Conserved interactions with stromal and immune cells coordinate de novo B cell lymphopoiesis in fetal intestines
Kimberly A. Carroll, Weihong Gu, Long Phan, Eduardo Gonzalez Santiago, Wenjia Wang, George C. Tseng, Liza Konnikova, Shruti Sharma
Kimberly A. Carroll, Weihong Gu, Long Phan, Eduardo Gonzalez Santiago, Wenjia Wang, George C. Tseng, Liza Konnikova, Shruti Sharma
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Research Article Development Immunology

Conserved interactions with stromal and immune cells coordinate de novo B cell lymphopoiesis in fetal intestines

Abstract

Recent findings suggest that the small intestine (SI) is a potentially novel site for B cell lymphopoiesis during fetal and neonatal life. However, the unique and/or conserved features that enable B cell development at this site remain unclear. To investigate the molecular and cellular scaffolds for B cell lymphopoiesis in mouse and human fetal intestines, we leveraged single-cell RNA-Seq, in situ immunofluorescence, spatial transcriptomics, and high-dimensional spectral flow cytometry. We found that SI mesenchymal and stromal cells expressed higher levels of chemokines known to recruit common lymphoid progenitors. Importantly, local lymphatic endothelial cells expressed IL-7 and TSLP in proximity to IL-7R+ precursor B cells, likely promoting their differentiation in the SI. Notably, we found that fetal-derived lymphoid tissue inducer (LTi) cells were required for B cell development and localization in the SI, but not fetal liver. These findings identify a lymphoid tissue development–independent role for this immune cell in B cell development. Collectively, our data reveal a conserved intestinal B cell niche in mice and humans, challenging traditional models of lymphopoiesis. The identification of a requisite cellular/molecular scaffold for fetal B cell development allows future studies to test the importance of this de novo B cell lymphopoiesis to long-term immunity.

Authors

Kimberly A. Carroll, Weihong Gu, Long Phan, Eduardo Gonzalez Santiago, Wenjia Wang, George C. Tseng, Liza Konnikova, Shruti Sharma

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Figure 3

Epithelial and stromal cells express molecular signals that may support B cell development in fetal intestines.

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Epithelial and stromal cells express molecular signals that may support ...
(A) UMAP of scRNA-Seq data from publicly available MCDA E14.5 fetal intestines with cell populations identified by differential gene expression (Supplemental Figure 4). (B) Heatmap of differential gene expression between B cells and subsetted stromal cells using curated gene list of different receptor ligand pairs involved in bone marrow B cell development. (C) Representative multiplex RNAscope images of fetal mouse intestine (E18.5). The yellow square highlights the region magnified on the right. Blue circles denote cells, red circles denote Cd19+ and Rag2+ cell. Scale bar: 50 μm (left) or 5 μM (right). (D) Chord diagram depicting the predicted IL-2 family signaling interactions between sender and receiver populations with colors corresponding to the sender population (outer ring) and arrowheads pointing to the receivers based on total cells and highlighted receptor ligand pairs within the predicted interactions. (E) Immunofluorescence of representative mouse intestinal tissue from E18.5 mice showing nuclear stain DAPI (blue), B220-FITC (red), and LYVE1-AF555 (cyan) with a selected, zoomed ROI with arrowheads to identify B cells. (F) Measured distance to nearest LYVE1 LECs with dots corresponding to individual cell distances (n = 3) with mean distance highlighted by dotted line and reported percentages below and above the mean. (G) Human intestinal tissue (21 weeks gestational age) stained with RNA probes RAG1 (green), CD19 (white), and anti-LYVE1 antibody (red). (H) Nuclei counterstained with DAPI (blue) in an identical analysis to F in human tissue sections (n = 1). Scale bars: 50 µM (C), 200 µM (E), 170 µM (G).