CD4 and graft versus host disease: Therefore, extensive research has been focused on identifying other cellular components of the graft that could modulate donor T cells and reduce the risk and severity of GvHD without diminishing normal immunological functions, including NK (Yamasaki et al., 2003), B (Shimabukuro-Vornhagen et al., 2009), and CD4+CD25hiFoxP3+ T regulatory (Treg) cells (Pabst et al., 2007; Wolf et al., 2007).