The suppressive activity of CD4⁺CD25⁺ T lymphocytes is not mediated by IL-10 or TGF-β. Purified CD4⁺CD25^– and CD4⁺CD25⁺ T cells were cocultured as described in “Patients, materials, and methods” in the presence of 5μg/mL p24 protein alone or in the presence of 10 μg/mL anti–IL-10, anti–TGF-β, or both neutralizing antibodies for 5 days before adding 0.5 μCi/well (0.0185 MBq) [³H] thymidine. Percentage of inhibition was calculated as described in “Proliferation and suppression assays.” Results are expressed as mean (± SD) percentage of inhibition of proliferation (n = 3).