Acute IFN-I and IDO responses correlate with the transient induction of FoxP3⁺CD25⁺CD8⁺ T cells. Spearman rank correlations between IDO activity and plasma viral load (A), IDO activity and CD8⁺CD25⁺FoxP3⁺ T cells (B), IDO activity and SIV-specific T-cell proliferation (C), and IDO activity and CD4⁺ T-cell activation (D). AUCs were used for plasma viral loads, CD8⁺CD25⁺FoxP3⁺ T-cell numbers (days 9-42), and SIV-specific T-cell proliferation (days 1-100), to take into account the optimal periods of time covering acute dynamic changes in each of these parameters during primary infection. ART-treated macaques are represented by open symbols, whereas untreated macaques are represented by gray (50 AID₅₀ group) or black (5000 AID₅₀ group).