CD4 and lymphopenia: Compared to findings among ART only controls, FTY720+ART: (i) induced a profound lymphopenia while increasing the frequency of cytolytic CD8+ T cells and NK cells within the LN; (ii) did not increase pVL decay at ART initiation and did not reduce the establishment nor the persistence of the intact SIV reservoir during ART; and (iii) resulted in a modest delay of viral rebound (4 days) and a reduced SIV-DNA content in CD4+ Tfh cells in a subset of animals after ATI.