Session: 701. Experimental Transplantation: Basic and Translational: Poster II
Hematology Disease Topics & Pathways:
Research, Translational Research, GVHD, Diseases, Immune Disorders, immunodeficiency, immunology, Biological Processes, Study Population, Animal model
We used a sublethal allo-HCT model with a low T cell dose that allowed for long-term survival over 100 days after transplantation (B6 into lethally irradiated B6xBALB/c F1 mice, 2x 5.5 Gy). Unlike allo-HCT recipients of T cell-depleted bone marrow (no GVHD control), recipients of T cell-depleted bone marrow plus allo-T cells (1-5x106 splenocytes) developed low-grade systemic GVHD with mild reversible weight loss. At day 30-60 after transplantation, allo-T cell recipients showed modestly decreased thymopoiesis, consistent with the thymus being a sensitive target organ of GVHD, as previously reported. In contrast to this mild injury, peripheral lymph nodes (pLN) showed profound long-lasting depletion of CD31-/podoplanin+ fibroblastic stromal cells as assessed by flow cytometry. Among these cells, MAdCAM-hi marginal reticular cells (MRCs) and CD157-hi fibroblastic reticular cells were most severely affected, including most cells lineage-traced by a Ccl19-Cre transgene. Total blood endothelial cells and lymphatic endothelial cells (LECs) were only modestly decreased by GVHD at day 30, but the LEC subset characterized by high MAdCAM expression consistent with a floor LEC phenotype virtually disappeared. Thus, MRCs and floor LECs lining the marginal sinus were severely affected by GVHD, suggesting that antigen uptake and processing could be defective in these pLN. Single cell RNA-seq revealed a near complete loss of floor LECs, MRCs and Ccl19/Ccl21+ T zone FRCs in GVHD-affected pLNs. Instead, residual fibroblastic stromal cells showed accumulation of collagen-expressing Cxcl14+ fibroblasts with loss of immune-interacting properties. In terms of functional consequences, GVHD pLNs had a markedly decreased abundance of naïve B and T cells, the latter despite relatively preserved naïve T cell production in the thymus. Compared to pLNs, the spleen was less profoundly affected and remained more receptive than pLNs to homing of adoptively transferred T cells. Immune responses to SARS-CoV2 mRNA used as a potent and clinically relevant T-dependent antigen were profoundly impaired in GVHD pLNs.
In summary, our data suggest that specialized fibroblastic stromal cells and LECs in secondary lymphoid organs are even more sensitive to GVHD than thymic epithelial cells, with little evidence of functional recovery. We speculate that subclinical damage to pLN stromal compartments may underlie many aspects of immune dysregulation in chronic GVHD, including persistently impaired responses to vaccination and loss of peripheral tolerance.
Disclosures: Maillard: Genentech: Research Funding; Regeneron: Research Funding; Garuda Therapeutics: Consultancy.
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