Figure 1.

Analysis of spleen T cells and pathology during longitudinal SIV infection. Pigtailed macaques were inoculated with an immunosuppressive swarm and a neurovirulent clone of SIV. A: Peripheral blood was obtained from SIV-infected macaques and RNA isolated at 4, 7, 10, 14, 21, 56, and 84 dpi to determine plasma viral load (open squares) by quantitative RT-PCR. CD4 T lymphocytes (closed circles) were enumerated in whole blood by flow cytometry. The acute (light shading), asymptomatic, and chronic (dark shading) phases of SIV infection are depicted. B–D: Single cell suspensions were obtained from spleen at 7, 21, 56, and 84 dpi and cells analyzed by flow cytometry. B: The frequency of CD8 (open squares) and CD4 T lymphocytes (closed circles) relative to the total spleen CD3 T lymphocyte population was determined by fluorescence-activated cell sorter analyses. C: The percentage of splenic CD4 T lymphocytes that expressed cell surface CD69 was examined in uninfected animals and at 7, 21, 56, and 84 dpi, as an indicator of cellular activation. D: The frequency of CD28⁺ naïve (gray bars), CD95⁺ effector memory (white bars), and CD28⁺CD95⁺ central memory (black bars) CD4 T lymphocytes in the spleen was determined by flow cytometry in uninfected macaques and at 7, 21, 56, and 84 dpi. E: Representative hematoxylin and eosin–stained spleen sections from uninfected and SIV-infected macaques euthanized at 4, 10, 21, 56, and 84 dpi. Solid lines connecting data points denote cumulative and longitudinal blood sampling of the same animals at every time point after inoculation. Dashed lines connecting data points indicate cross-sectional study of independent groups of animals after euthanasia at each time point. Statistical significance was determined by Mann-Whitney test. Data are expressed as means ± SD. ^∗P ≤ 0.05 versus the preceding day after inoculation. Original magnification, ×2 (E). Eq, equivalents.