In this regard, many factors involved in CD4+ recovery have been described, among which include age, low CD4+ T-cells nadir, severe immunodeficiency at the time of cART initiation, low baseline CD4/CD8 ratio, immune exhaustion, abnormal immune activation, reduced output in the bone marrow and thymic, increased senescence and apoptosis of T-cells, lymphoid tissue fibrosis, imbalance in Treg and Th17 cells, microbial translocation, persistent HIV replication, and host genetic background, among others (Yang et al., 2020). Here, CD4 is linked to immunodeficiency disease.