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Kidney Week

Abstract: TH-OR79

MIF-CD74: A Novel Inflammatory Pathway that Suppresses Allograft-Infiltrating Tregs During Rejection

Session Information

Category: Transplantation

  • 2101 Transplantation: Basic

Authors

  • Younis, Nour Khaled, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Solhjou, Zhabiz, Scripps Green Hospital, La Jolla, California, United States
  • Zhang, Hengcheng, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • El Kurdi, Abdullah Bilal, American University of Beirut, Beirut, Lebanon
  • Halawi, Ahmad, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Bucala, Richard, Yale School of Medicine, New Haven, Connecticut, United States
  • Zhang, Dongliang, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Azzi, Jamil R., Brigham and Women's Hospital, Boston, Massachusetts, United States
Background

We previously showed that CD74, a key receptor of MIF, a pro-inflammatory cytokine, is upregulated in the urinary exosomal mRNAs of kidney transplant recipients during rejection. We investigated this pathway in allo-immunity and discovered a previously unknown critical role in suppressing immune regulation.

Methods

CD74KO (KO), and CD74fl/fl-Foxp3-GFP-Cre C57BL/6J mice were generated using CRISPR-Cas9 technology and used as recipients for fully mismatched BALB/c heart transplants. We performed single-cell and bulk RNA sequencing, CHIP-seq, immunophenotyping using flow cytometry, and various ex-vivo studies to assess the impact of the MIF-CD74 pathway on Tregs Homeostasis.

Results

CD74KO recipients of fully mismatched heart allograft displayed indefinite allograft survival with a 3-fold increase in allograft-infiltrating Tregs, compared to WT. While naïve Tregs and Tregs in the spleen of WT recipients did not express CD74, Tregs infiltrating the heart allograft and dLN and Tregs stimulated in vitro upregulated CD74 up to 5-fold. Furthermore, conditional deletion of CD74 in Tregs doubled allograft survival while resulting in a 2-fold increase in allograft-infiltrating Tregs. Moreover, compared to WT, KO Tregs displayed enhanced proliferative capacity, increased FoxP3 stability, and improved suppressive function in vitro and in vivo. Furthermore, MIF was predominantly produced by CD4 and CD8 effector cells upon antigen stimulation in vitro and in vivo. Congruently, our single-cell genomic analysis performed on allograft-infiltrating T cells endorsed the superior suppressive phenotype of CD74 deficient Tregs. While allograft-infiltrating WT Tregs had an interferon-responsive phenotype, KO Tregs had a KLRG1+Areg+ phenotype with higher Helios and PD1 expression. Our TCR clonal analysis also suggested that allograft-infiltrating KO Tregs are more antigen-specific. Furthermore, our genomic analysis revealed that Interferon Regulatory Factor 1 (IRF1), a transcriptional repressor of FoxP3, is downregulated in allograft-infiltrating KO Tregs. In vitro, MIF activates IRF1 in WT but not KO Tregs.

Conclusion

MIF produced by effector T cells in response to alloantigens negatively affects Tregs function and homeostasis via CD74 signaling. The MIF-CD74 pathway exerts this effect through IRF1.