IDO1 and systemic lupus erythematosus: In an elegant study, they determined that high levels of interferon-γ, produced predominantly by CD8+ T-cells in SLE patients, are a key factor involved in the stimulation of allogeneic ucMSC to produce indolamine 2,3-dioxygenase, which can then inhibit the proliferation of T-cells from SLE patients [128].