To investigate whether anti‐P2X7 Nbs can attenuate GVHD in a humanised mouse model, NSG mice were injected i.m. with AAV vectors encoding either green fluorescent protein (GFP), anti‐mP2X7 (13A7) or anti‐m/hP2X7 (1C81) Nbs (10 × 1010 viral genomes per mouse), or an equal volume of saline at Day −21. Here, P2RX7 is linked to graft versus host disease.