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1326 TNFα-Driven Interplay between Hematopoietic Stem Cells and Antigen-Specific Cytotoxic T Cells

Program: Oral and Poster Abstracts
Session: 503. Clonal Hematopoiesis, Aging and Inflammation: Poster I
Hematology Disease Topics & Pathways:
Research, apoptosis, Fundamental Science, CHIP, hematopoiesis, immunology, Biological Processes, molecular biology
Saturday, December 9, 2023, 5:30 PM-7:30 PM

Zhiqian Zheng, MS1*, Akiho Tsuchiya, PhD1*, Emmanuelle A. Passegue, PhD2, Atsushi Iwama, MD, PhD1 and Masayuki Yamashita, MD, PhD3

1Division of Stem Cell and Molecular Medicine, Center for Stem Cell Biology and Regenerative Medicine, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan
2Columbia Stem Cell Initiative, Department of Genetics & Development, Columbia University Irving Medical Center, New York, NY
3The University of Tokyo, Tokyo, TKY, Japan

Clonal hematopoiesis (CH) is governed by aberrant hematopoietic stem cell (HSC) clones with leukemia-associated somatic mutations that arise spontaneously during organismal aging or after exposure to genotoxic insults. Cells with a somatic mutation can be eliminated through presentation of neoantigens on MHC class I (MHC-I) to antigen-specific cytotoxic T cells. Indeed, many of the CH-related mutations, such as JAK2V617F, are reported or predicted to elicit antigen-specific cytotoxic T cell response. On the other hand, accumulating evidence suggests that inflammatory environment facilitates clonal expansion of abnormal HSCs. However, much remains to be elucidated on whether HSCs expressing such non-self peptides can be eliminated by antigen-specific cytotoxic T cells and how inflammation affects the T cell-mediated HSC regulation.

Our RNA-seq analyses revealed that genes involved in MHC-I-dependent antigen presentations, such as Nlrc5, H2-kb and B2m, are most abundantly expressed in HSCs (Lin-/c-Kit+/Sca-1+/Flk2-/CD48-/CD150+) among murine bone marrow immature hematopoietic cells. Using transgenic mice that ubiquitously express a model antigen ovalbumin (OVA) and a monoclonal antibody that specifically recognizes MHC-I-OVA complex, we found that while MHC-I protein is abundantly expressed on the surface of hematopoietic cells except granulocytes, HSCs and multipotent progenitor cells (MPPs) possess greater capacity to present intracellular antigens through MHC-I compared to myeloid progenitor and mature cells. Remarkably, in vitro co-culture experiments revealed that whereas OVA-expressing (OVA+) HSCs, MPPs and myeloid progenitors could directly activate OVA-specific OT-I CD8+ T cells through MHC-I-dependent antigen presentation, HSCs are the most susceptible population to the killing effect by cytotoxic T cells. Indeed, co-infused OT-I CD8+ T cells totally abolished the long-term repopulation capacity of OVA+ HSCs in a serial transplantation setting, and adoptive transfer of OT-I CD8+ T cells to mixed chimeric mice that harbor both wild-type and OVA+ hematopoietic cells completely and specifically eliminated hematopoiesis governed by OVA+ HSCs.

TNFα is not only a prototypical inflammatory cytokine but also one of the major cytokines that are secreted by CD8+ cytotoxic T cells. Notably, genes directly involved in T cell regulation including Cxcl9, Cd274, and Pdcd1lg2 were induced in HSCs, but not myeloid progenitor cells, upon exposure to TNFα (Yamashita and Passegué, Cell Stem Cell 2019). Indeed, upon co-culturing OT-I CD8+ T cells produced TNFα as well as IFNγ and Granzyme B and OVA+ HSCs but not myeloid progenitor cells produced CXCL9 largely in a TNFα receptor-dependent manner. Interestingly, such HSC response to T cell-derived TNFα was critical for naïve CD8+ T cells to rapidly differentiate to effector cytotoxic T cells, as TNFα receptor-deficient (Tnfr1-/-Tnfr2-/-) OVA+ HSCs stimulated proliferation and cytokine production of OT-I CD8+ T cells but failed to stimulate Granzyme B production, whereas IFNγ receptor deficiency (Ifngr-/-) did not have such effect. As a result, Tnfr1-/-Tnfr2-/- OVA+ HSCs, but not Ifngr-/- OVA+ HSCs, could escape from the killing by OT-I CD8+T cells. In sharp contrast, prior exposure to environmental TNFα, but not to IL-1β or IL-6, before interaction with OT-I CD8+ T cells rendered OVA+ HSCs resistant to the killing by OT-I CD8+ T cells largely through upregulation of PD-L1 and PD-L2. Of note, upon 24-month aging or acquisition of Jak2V617F mutation, OVA+ HSCs still maintained robust MHC-I-dependent antigen presentation activity and high susceptibility to the killing by OT-I CD8+ T cells, though prior exposure to TNFα allowed for their immune escape. Consequently, adoptive transfer of OT-I CD8+ T cells completely and specifically eliminated Jak2V617F-mutant OVA+ HSCs and reversed myeloproliferative neoplasms in the mixed chimeric mice.

Taken together, our results reveal the robustness of HSC quality control via MHC-I-dependent antigen presentation to antigen-specific cytotoxic T cells. They also highlight a critical but complex role of TNFα in active interplay between HSCs and antigen-specific cytotoxic T cells as well as immune evasion by HSCs during inflammation. Specifically targeting abnormal HSCs by antigen-specific cytotoxic T cells may pave the way to eradicate mutant HSC clones and prevent CH-associated disease.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH