Session: 701. Experimental Transplantation: Basic Biology, Pre-Clinical Models: Poster III
Hematology Disease Topics & Pathways:
Biological Processes, immune mechanism
Methods: We used both IL-33 knockout mice as recipients and ST2 (IL33 receptor) knockout mice as T cell donors in MHC mismatch alloSCT models to define the spatial and temporal importance of IL-33 in GVHD tissue damage. More specifically, to establish the role of IL-33 in T cell effector function in the small intestine during GVHD, irradiated Il33-/- and Il33+/+ C57BL/6 (B6) recipients were given BALB/c bone marrow (BM) and T cells. Additionally, irradiated BALB/c mice were given St2+/+ B6 BM and Cd4 Cre x St2fl/fl or St2-/- and St2+/+ T cells. To determine the role of IL-33 on T cell persistence in GVHD, we used an MHCII-disparate model. Irradiated Il33-/- and Il33+/+ bm12 recipients were reconstituted with B6 BM, with or without CD90.1+ B6 T cells.
Results: When donor T cell responses were characterized by flow cytometry at days 7, 14, and 28 post alloSCT, the bulk of these data suggest that IL-33 sustains CD4+ T helper Type 1 (Th1) cells in the barrier tissues at late points following GVHD initiation. Specifically, B6 Il33-/- recipients had fewer BALB/c CD4+Tbet+ cells in the small intestine lamina propria (SI LP; WT 15.9 ± 1.31, KO 9.53 ± 1.32; p=0.03; n=3/group), but not in the spleen (WT 54.8 ± 7.37, KO 57.68 ± 4.90; p=0.75; n=4/group) at day 7. Additionally, we found that when we used therapeutic doses of anti-IL-12p40 to neutralize IL-12 there was no impact on the CD4+Tbet+ cells in the SI of B6 il33-/- recipients (KO control IgG 7.29 ± 0.63, KO anti-IL-12p40 6.61 ± 0.75; p=0.52; n=4/group) suggesting that the decrease in the frequency of CD4+Tbet+ T cells in Il33-/- in the SI is independent of IL-12. In the CD4-dependent B6 to bm12 GVHD model, we find that IL-33-deficient recipients have reduced overall CD4+ donor T cells in the SI LP at both day 14 and day 28 (d14: WT 16.15 ± 2.55, KO 0.35 ± 0.07; p=0.003; n=3/group; d28: WT 33.07 ± 7.17, KO 6.27 ± 1.59; p=0.022; n=3/group). Consistent with our B6 recipients of BALB/c T cells above, this decrease was not observed in the spleen or lymph nodes. Reduced clusters of CD3+ cells were evident in immunohistochemistry of bm12 Il33-/- relative to bm12 Il33+/+ at day 28 post-alloSCT. In corroboration with our IL-33-deficient recipient results, B6 CD4+ T cells lacking the ST2 receptor when co-transferred with ST2 competent T cells were not sustained in the SI LP at day 7 (ST2 WT 18.55 ± 0.77, ST2 KO 6.35 ± 1.42; p=0.0003; n=4/group). ST2 deficient CD4+ donor cells were of equal frequency to the ST2 competent donor cells in the spleen of BALB/c recipients (ST2 WT 54.58 ± 1.914, ST2 KO 50 ± 2.53; p=0.19; n=4/group).
Conclusions: Our data reveal that IL-33 is not required for donor Th1 responses in the spleen and LN, but IL-33 is critical for Th1 cells to persist in barrier tissues like the small intestine after alloSCT in the absence of IL-12 stimulation. These data suggest that targeting IL-33 signaling may be an effective therapy to diminish GVHD in target tissues.
Disclosures: Blazar: Fate Therapeutics Inc.: Research Funding; Childrens' Cancer Research Fund: Research Funding; BlueRock Therapeutics: Research Funding; BlueRock Therapeuetic: Consultancy; Magenta Therapeutics: Consultancy; KidsFirst Fund: Research Funding; Tmunity: Other: Co-founder. Shlomchik: Bluesphere Bio: Consultancy, Other: shareholder.
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