Figures 2 and 3 summarizes these approaches. It has been established that CD4 Tregs require IL-2, TGF-β, and continuous T cell receptor stimulation for function and survival (7, 32, 33). Nanoparticles can provide these agents and, where possible, the antigen for the generation of antigen-specific Tregs. Also, although most investigators have focused on CD4 Tregs, CD8 Tregs have as well important tolerogenic roles (34, 35). In human SLE, like CD4 Tregs, CD8 Tregs can inhibit anti-DNA autoantibodies (36, 37). Here, CD4 is linked to systemic lupus erythematosus.