The largest module that correlated with GVHD target organs was M27, which segregated mainly with the LP; this cluster was enriched for multiple intracellular signaling gene pathways including MAPK (e.g., Map3k1 and Relb) and JAK-STAT (e.g., Jak2, Stat3, and Stat5a). This evidence concerns the gene STAT5A and graft versus host disease.