IL21 and systemic lupus erythematosus: Strong proinflammatory conditions can transform Treg cells into cells that produce IL17 or other inflammatory cytokines, and, as has been suggested, CAR-Treg cells may be effective in the treatment of SLE under the condition of eliminating the influence of inflammatory cytokines, such as IL6, IL21 and IFNɑ, which inhibit Treg activity [81].