Schematic representation of different factors influencing the development of GVHD. In full HLA-matched allogeneic HCT, minor H antigens disparities between donor and recipient are associated with severe GVHD. CTL, cytotoxic T lymphocyte; mRNA, messenger RNA; TCR, T-cell receptor. See Figure 1A in the article by Sato-Otsubo et al that begins on page 2752.