Selective lymphopenia in mice with a B- or a T-cell–specific IFNAR deletion. (A) Poly(I:C) or PBS-treated splenocytes of the indicated mice were analyzed by FACS for the IFN-α/β–dependent markers CD69 on B cells and Ly6C on T cells. Note the lack of up-regulation of CD69 on B cells in CD19-Cre^+/–IFNAR^flox/flox mice and of Ly6C on T cells in CD4-Cre^+/–IFNAR^flox/flox mice, indicating selective and quantitative IFNAR inactivation in the respective lymphocyte subsets. Representative data of 2 experiments are shown. (B) CD19-Cre^+/–IFNAR^flox/flox and CD4-Cre^+/–IFNAR^flox/flox mice were given injections of poly(I:C) or PBS. Blood lymphocyte counts were determined before and after treatment. Individual results of 25 CD19-Cre^+/–IFNAR^flox/flox and 13 CD4-Cre^+/–IFNAR^flox/flox mice are shown. (C) BL/6, CD19-Cre^+/–IFNAR^flox/flox, and CD4-Cre^+/–IFNAR^flox/flox mice were treated with 2 × 10⁵ IU IFN-α, and lymphocyte counts were determined before and after treatment. Data are expressed as mean ± SD remaining cell percentages in blood. Representative data of 3 experiments with 2 to 4 mice per group are shown. (D) BL/6, CD19-Cre^+/–IFNAR^flox/flox, CD4-Cre^+/–IFNAR^flox/flox, IFNAR^–/–, and TNF-α^–/– mice were treated with R-848. Numbers of B and T cells were counted before and after injection. Data are expressed as mean ± SD of percentages of remaining cells in blood. Experiments were performed 4 times, twice with TNF-α^–/– mice, with 2 to 4 mice per group.