Mechanistic interventions for the prevention or treatment of chronic GVHD. Current and new approaches for the prevention or treatment of chronic GVHD primarily target alloreactive donor T cells, allo- and autoreactive B cells, or CD4⁺FoxP3⁺ regulatory T cells. As advances in our understanding of the role of each of these cell types in the development of chronic GVHD has advanced in recent years, it is now possible to develop and select for clinical testing a variety of therapeutic interventions that focus on specific mechanistic pathways. Professional illustration by Patrick Lane, ScEYEnce Studios.