The percentage of major lymphocyte populations does not change significantly during the course of recombinant IFN-α treatment of SIV-infected SMs but the numbers of CD8 T cells do decrease significantly between days 7 and 21 of treatment. Shown are counts and percentages of the major lymphocyte populations as determined by flow cytometry. (A) CD4⁺ T-cell counts. (B-D) % CD4⁺ T cells in blood (B), LNs (C), and RBs (D). (E) CD8⁺ T-cell counts. (F-I) %CD8⁺ T cells in blood (F), LNs (G), and RBs (H). (I) CD16⁺CD8⁺ natural killer (NK) cell counts. (J) CD20⁺ B-lymphocyte counts. Differences were determined using the Friedman test with Dunn multiple comparisons. *P < .05; **P < .01; ***P < .001.