In a recent report by Ali et al., human CD4+ T cells were engineered to express the R164 TCR clone, and importantly, when administered to NSG-Ab0 DRB*04:01 mice, these R164 cells established long-term engraftment and islet infiltration, up to 12 weeks, without graft versus host disease (GvHD) (25). The gene discussed is CD4; the disease is graft versus host disease.