Biomarker assays with a high predictive value at the onset of a-GVHD include single cytokines, such as soluble suppression of tumorigenicity-2 (sST-2), a protein encoded by the IL1RL1 gene; interleukin 6 (IL-6); soluble interleukin-2 receptor (sIL-2R); and soluble tumor necrosis factor receptor 1 (sTNFR1) (4–6). Here, IL6 is linked to graft versus host disease.