FIG. 9.

CD8⁺ IFN-γ mRNA is reduced in FIV⁺ cats by TGF-β treatment and following coculture with CD4⁺CD25⁺ Tregs. In all, 2–4 × 10⁶ purified CD8⁺ lymphocytes from FIV^– (gray bars) or FIV⁺ (dark bars) cats were serum starved overnight and were either untreated, treated with TGF-β, or cocultured with CD4⁺CD25⁺ Tregs, and RNA from CD8⁺ cells was then harvested for determination of IFN-γ mRNA by RT-PCR. For the CD4⁺CD25⁺/CD8⁺ cocultures, CD4⁺CD25⁺ cells were depleted by magnetic bead separation prior to RNA collection. The CD8⁺ cells were either untreated, Con A (5 μg/ml) stimulated for 30 min followed by TGF-β (10 ng/ml) for 120 min, or treated with Con A for 30 min followed by coculture with CD4⁺CD25⁺ cells (1:1 ratio) for 120 min. In FIV⁺ cats, there was a significant reduction in IFN-γ mRNA following coculture with CD4⁺CD25⁺ Tregs (p < 0.05, asterisks). Each bar represents the mean ± SEM from five experiments.