The gut microbial metabolite N-oxide trimethylamine exacerbates GVHD by inducing the polarization of mouse M1 macrophages and increasing the expression of pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α [55].Ultimately, these findings underscore IL-1β as a central mediator in GVHD pathogenesis, providing new molecular insights into the pathogenesis underlying autoimmune diseases [28]. The gene discussed is IL1B; the disease is graft versus host disease.