FIG. 2.
High levels of biologically active IFN are present in the serum of VRP-infected mice. Adult BALB/c mice were inoculated in the RRFP with 2 × 106 IU of null VRP. At 1, 3, 6, 12, or 24 h following inoculation, the mice were euthanized, followed by cardiac puncture and exsanguination to collect blood samples. Type I IFN present in the serum was measured by standard IFN biological assay on L929 cells, and the results are presented as IU per milliliter. Each bar represents an individual animal, with the limit of detection (LOD) for the assay indicated by a dotted line. The data in this and the previous figure correspond to the same group of mice.