Clearance of LCMV-ARM and LCMV-WE by thymus-derived and extrathymic T cells. (A) Mean virus titers (log pfu/organ) in the spleen, mLNs, and lung of B6 mice (□), OM → RAG1-/- chimeras (▴), and RAG1^-/- mice (•) following LCMV-ARM infection. There were 3 mice per group. (B) Mean virus titers (log pfu/organ) in mice infected with LCMV-WE. Spleen, kidney, and lung of B6 mice (○) and OM → RAG1-/- chimeras (▦) were harvested on days 8 and 20 after infection. Two to 3 mice were in each group. In panels A and B, dotted lines indicate the detection limit of the immunologic focus assay. (C) Apoptosis of splenic CD8 T cells following LCMV-ARM infection. Histogram bars show the mean proportion of annexin V⁺ elements among GP33 tetramer-positive (+) and tetramer-negative (-) CD8 T cells in B6 mice (black and dark gray bars) and OM → RAG1^-/- chimeras (white and light gray bars); 3 to 4 mice per group.