STAT6 and graft versus host disease: In the complex in vivo ecosystem after BMT, in which several other variables have an effect on the outcome (for example, gut microbiome composition influencing the predisposition to GVHD [42], vitamin D promoting Th2 maturation in a STAT6-dependent manner [43] and coordinating immune reactivity with the microbiome [44]), further characterization of the function of STAT6 in T cell immunity merits further exploration.