FIG. 1.

Kinetics of intedeukin-10 (IL-10) exposure on the immune response against recombinant vaccinia virus is graphically illustrated here. BALB/c mice were injected intravenously with 10⁷ plaque-forming units (PFU) of VJS6 atone (-) or VJS6 followed by IL-10 (I μg i.p.) 12 hours later and continued daily for 5 days (—). Two mice from each group were killed every other day after collection of serum for antibody titers, extraction of the visceral organs for viral titers, and harvesting of splenocytes for chromium release assays. Virus was, cleared more rapidly from the ovaries after IL-10 treatment (A) with titers less than 10³ PFU in the kidneys, liver, and lungs (not shown); anti-vaccinia antibody titers, as measured by anti-vaccinia enzyme-linked immunosorbent assay, were not affected by IL-10 administration (B); anti-vaccinia cytotoxic T-cell (CTL) activity, determined by 8-hour chromium release assay against vaccinia-infected CT26.WT cells shown at an effector-to-target (E:T) ratio of 25:1, was increased after IL-10 exposure (C) with minimal natural killer cell activity, as measured in an 8-hour chromium release assay against YAC-1 cells shown at an E:T ratio of 25:1 (not shown). The peak CTL activity correlates with the rapid clearance of virus seen by the 6th day of treatment. These experiments were all repeated with nearly identical results.