Nanographene Oxide Attenuates Acute GVHD by Modulating Macrophage Polarization in a Xenogeneic Mouse Model

Nanographene oxide (NGO) exhibits immunomodulatory activity and holds promise as a therapeutic agent for graft‐versus‐host disease (GVHD). In a xenogeneic GVHD mouse model, NGO administration improves survival and attenuates pathology with reduced weight loss and leukocyte engraftment, without sustained systemic toxicity. In GVHD patient‐derived peripheral blood mononuclear cells (PBMCs), NGO treatment shifts T cell subsets toward immune homeostasis by increasing naïve T cells and decreasing effector memory T cells. Integrated transcriptomic analyses of PBMCs from GVHD patients and healthy donors reveal downregulation of pro‐inflammatory and interferon‐gamma–signal transducer and activator of transcription 1 (IFN‐γ–STAT1)–associated genes, coinciding with the suppression of M1 macrophage signatures and induction of anti‐inflammatory profiles. Mechanistically, NGO inhibits STAT1 activation and biases macrophages toward an anti‐inflammatory state, independent of reactive oxygen species scavenging and lipopolysaccharide–myeloid differentiation primary response 88 (LPS–MyD88) signaling. To improve translational feasibility, NGO‐primed macrophages (NGO‐Mac) are generated, which produce higher levels of interleukin‐10 (IL‐10), inhibit helper T cell 1 (Th1) differentiation, and promote regulatory T cell (Treg) induction in an IL‐10–dependent manner. In vivo, NGO‐Mac therapy reduces M1 macrophage infiltration, increases Treg frequencies, and attenuates GVHD pathology. These findings highlight NGO and NGO‐Mac as complementary immunotherapies, while further studies on safety, biodistribution, and feasibility are necessary for translation.