Mechanisms behind soluble and insoluble CXCL13 chemokine gradients in secondary and tertiary lymphoid tissues 3111

Abstract Description This study investigates the spatial organization and the mechanisms responsible for forming soluble and insoluble CXCL13 chemokine gradients. CXCL13 attracts B-cells to follicles in secondary lymphoid tissue and tertiary lymphoid structures (TLS). Cosgrove’s et al. ex vivo tonsil tissue studies showed that CXCL13 forms a soluble and insoluble chemokine gradient via immobilization in the extra cellular matrix. Mechanisms of CXCL13 secretion, immobilization and spatial distribution are unknown. Quantitative CXCL13 IHC/ISH co-stain analysis in human tonsil demonstrates abundant CXCL13 mRNA in mantle zone compared to germinal center cells (p < 0.0001). However, more CXCL13 protein localizes in germinal center compared to mantle zone cells (p < 0.0001). Flow cytometry confirmed CXCL13 presence on PDPN+ CD31- stromal cells in tonsil. The ISH tissue staining pattern was validated and candidate genes responsible for CXCL13 immobilization were identified using public spatial and single-cell transcriptomics datasets. Lung cancer TLS showed a similar IHC/ISH tissue staining pattern. Additionally, we found that CXCL13 is immobilized by elastin fibers surrounding TLS. This study uncovers potential mechanisms regulating CXCL13 chemokine gradients. Enhancing intratumoral CXCL13 gradients may create a more favorable tumor microenvironment which could improve the effectiveness of immune based anti-cancer therapies. Funding Sources Supported by R01CA142779 from NCI & Mark Foundation for Cancer Research Topic Categories Cytokines and Chemokines and Their Receptors (CCR)