To verify whether IL-21 accelerates EBV-positive DLBCL cell proliferation in vivo, we established a NOD/SCID mouse xenograft model of EBV-positive DLBCL by subcutaneous inoculation of Farage cells and measured tumour growth after IL-21 (10 μg) treatment once daily for 7 consecutive days. This evidence concerns the gene IL21 and diffuse large B-cell lymphoma.