In contrast, STAT3–/– spleen or T cells induced only mild and transient or reversible acute GVHD with no evidence of chronic GVHD, and all recipients (10/10) survived for more than 100 days (Figure 1A and Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/JCI165723DS1). This evidence concerns the gene STAT3 and chronic graft versus host disease.