Wysocki et al.42demonstrated that irradiated mice transferred with CCR5−/− T cells had an earlier time to onset and worsening GVHD compared to nonirradiated recipients due to higher expression of pro‐inflammatory chemokines such as CXCL10 and CXCL11 which were responsible for CCR5−/− T cell migration to target tissues. The gene discussed is CCR5; the disease is graft versus host disease.