Figure 4.

Relative levels of IFN-γ mRNA in CD4⁺ T cells from naive or C. albicans–infected IL-4^+/+ and IL-4^−/− mice. Mice were infected with 10⁶ PCA-2 intravenously and reinfected with 10⁶ virulent CA-6 14 d later. Cells were purified from spleens at 3 d after reinfection. *, Mice were infected as above and treated with rIL-4 (3 μg/each injection) on days 6, 8, 10, and 12 after PCA-2 infection. Semiquantitative competitive PCR was performed as described by Reiner et al. (30). Photographs are shown of ethidium bromide–stained gels of representative PCR reactions using HPRT– and IFN-γ–specific primers in the presence of serial fivefold dilutions of the experimental sample and a fixed concentration of the competitor, as described in Materials and Methods. The upper band was due to amplification of the competitor construct and the lower band was due to amplification of cDNA. The point of equivalence in intensity between the competitor and cDNA indicates the relative concentration of mRNA. The relative concentration of HPRT was used to control differences in mRNA concentration and efficiency of cDNA synthesis.