Chemokines guiding the migration of T cells toward GVHD target organs (40) wherein activated T cells mediate targeted tissue cell death via FAS ligand, perforin/granzymes, and releasing pro-inflammatory mediators mainly tumor necrosis factor (TNF-α), interferon (IFN-γ) (5, 41, 42). The gene discussed is TNF; the disease is graft versus host disease.