IL2 and graft versus host disease: Another promising IL-2 variant with site-specific PEGylation, designated dual 31/51-20 K, similarly displayed substantially increased clearance half-life, preferentially stimulated Treg over effector T cells compared with unmodified IL-2 by selectively reducing the binding affinity for the β subunit of IL-2R, and significantly reduced disease activity and severity in mouse models of xenogeneic graft-versus-host disease (GvHD), SLE and collagen-induced arthritis.