FIG. 4.

In vivo CTL activity against GagL peptide-presenting splenocytes in infected/treated/nondepleted mice. Splenocytes were prepared from noninfected mice and either (i) loaded with the GagL peptide and labeled with 10× CFSE or (ii) loaded with the np396-404 LCMV NP-derived peptide and labeled with 1× CFSE. The two populations were then mixed in an approximately 1:1 ratio and administered intravenously to either naive (control) or infected/treated/nondepleted 2-month-old mice. Sixteen hours later, splenocytes from grafted mice were purified and analyzed by flow cytometry for CFSE fluorescence. A reduction of 10× CFSE-labeled cells in infected/treated/nondepleted mice but not in control mice is indicative of CTL activity against infected splenocytes. (A) Flow cytometry analysis. Two representative control and two representative infected/treated/nondepleted mice are presented. Splenocytes were analyzed for CFSE fluorescence as described in Materials and Methods. (B) Statistical representation of data. The histograms correspond to the analyses of 12 mice each. The CTL activity against GagL-loaded splenocytes was calculated from the ratio of CFSE^high/CFSE^low cells 16 h after adoptive transfer corrected by the CFSE^high/CFSE^low ratio assayed before grafting cells into the recipient mice. Error bars correspond to the standard deviation.