Since Dsg3-specific CD4+ T cells can be detected in PV patients with an MHCII tetramer (45), the recent discovery of a compound that converts effector T cells to Tregs by inhibiting CDK8/19 in mice (46) would make possible the preparation of Dsg3-specific Tregs for antigen-specific Treg therapy of PV. The gene discussed is CD4; the disease is acquired polycythemia vera.