IL-33 acts as a costimulatory signal to generate alloreactive Th1 cells in graft-versus-host disease

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Abstract

Antigen-presenting cells (APC) integrate signals emanating from local pathology and program appropriate T cell responses. In allogeneic hematopoietic stem cell transplantation (alloHCT), recipient conditioning releases Damage-Associated Molecular Patterns (DAMPs) that generate pro-inflammatory APC that secrete IL-12, which is a driver of donor Type 1 T helper (Th1) responses causing graft vs. host disease (GVHD). Nevertheless, other mechanisms exist to initiate alloreactive T cells responses, as recipients with disrupted DAMP signaling or lacking IL-12 develop GVHD. We established that tissue damage signals are perceived directly by donor CD4+ T cells and promoted T cell expansion and differentiation. Specifically, the fibroblastic reticular cell-derived DAMP, IL-33, is increased by recipient conditioning and is critical for the initial activation, proliferation, and differentiation of alloreactive Th1 cells. IL-33-stimulation of CD4+ T cell was not required for lymphopenia-induced expansion, however. IL-33 promoted IL-12-independent expression of Tbet and generation of Th1 cells that infiltrated GVHD target tissues. Mechanistically, IL-33 augmented CD4+ T cell TCR-associated signaling pathways in response to alloantigen. This enhanced T cell expansion and Th1 polarization, but inhibited the expression of regulatory molecules like IL-10 and Foxp3. These data established an unappreciated role for IL-33 as a costimulatory signal for donor Th1 generation after alloHCT.

Authors

Gaelen K. Dwyer, Lisa R. Mathews, Jose A. Villegas, Anna Lucas, Anne Gonzalez de Peredo, Bruce R. Blazar, Jean-Philippe Girard, Amanda C. Poholek, Sanjiv A. Luther, Warren Shlomchik, Hēth R. Turnquist