<p>Naive SMARTA cells were CFSE-labeled and transferred either to mice that had been infected with LCMV two days previously, or to uninfected mice some of which were immediately infected with LCMV. A. 2, 3 or 4 days after cell transfer (as indicated), the spleens of the recipient mice were isolated and the donor SMARTA CD4<sup>+</sup> T cells were identified by flow cytometry (ovals). Individual mice are shown, and the numbers indicate the proportion of SMARTA cells as a percentage of all spleen cells. Mouse numbers in each of the 4 groups: 1, 1, 3, 3. B. The bar graph shows cumulative data, as percentages of SMARTA CD4<sup>+</sup> T cells. C. The histograms show the CFSE fluorescence of the indicated SMARTA CD4<sup>+</sup> T cells. Note that the 3-day delay in proliferation is shortened to 2 days if the mice were pre-infected.</p
