Thus, MDSCs do not play an immunosuppressive role in the early stage of AD, while with the progression of the disease, under the continuous effects of chronic inflammation, MDSCs induced the expressions of Arg-1 and indoleamine-pyrrole 2,3-dioxygenase (IDO) 1 by secreting anti-inflammatory factors IL-10 and TGF-β, inhibited the proliferations of inflammatory cells and exerted an immunosuppressive efficacy [53]. Here, ARG1 is linked to Alzheimer disease.