Immune activation and lymphoid system disruption upon HIV ssRNA treatment. Mice were treated intravenously with a mixture of uridine-rich HIV ssRNA (RNA U, 50 μg/mouse per day) or control RNA (RNA A) for 7 days. (A) HIV ssRNA treatment induced lymphopenia and increased relative monocyte and neutrophil numbers in 3 of 4 mice. Blood was analyzed 1 hour after the last injection. (B) Splenic lymphoid subpopulations from ssRNA-treated animals displayed an activated phenotype. CD69 expression was analyzed by flow cytometry. (C) Disruption of the lymphoid structure upon ssRNA treatment. There was malformation of splenic lymphoid follicles (CD4 and not shown) and reduced marginal zone B lymphocytes (CD21/35; arrowhead). (D) Relative contraction of CD4⁺ and CD8⁺ lymphoid subsets upon ssRNA treatment. Splenocytes were stained with indicated antibodies, and relative numbers were assessed by flow cytometry. (E) Splenomegaly upon ssRNA treatment. Spleen weight was first normalized to total body weight and, second, normalized to the spleen weight of mock-treated animals. Error bars indicate 95% confidence intervals. (F) Cytokine deregulation upon ssRNA treatment. Cytokine levels at day 7 are shown. Error bars indicate standard error. N = 4 for ssRNA-treated mice.