Theoretically, due to its role as a major regulator of T-lymphocyte homeostasis, IL-7 might be particularly helpful in patients on HAART with persistent CD4+ lymphopenia, but the actual clinical value of IL-7 treatment in these patients is questioned by the evidence of already elevated endogenous IL-7 levels and reduced IL-7Rα expression [16], [17], [28], [29]. This evidence concerns the gene CD4 and lymphopenia.