IVIg-treated human DCs but not monocytes expand Tregs. (A) DCs were cultured in GM-CSF and IL-4 alone (Ctr) or with IVIg (10 mg or 15 mg) or HSA for 24 hours. DCs were washed extensively and cocultured with CD4⁺ T cells for 4 days. Tregs (CD4⁺CD25⁺FoxP3⁺) were analyzed by flow cytometry. Representative dot blot of 8 independent experiments is shown. (B) Percentage (mean ± SEM, n = 8) of CD4⁺CD25⁺FoxP3⁺ cells in the DC-CD4⁺ T cell cocultures, *P < .05; **P < .01. (C) Circulating monocytes were cultured alone or with IVIg (15 mg) for 24 hours. Cells were washed extensively and cocultured with CD4⁺ T cells for 4 days. Tregs (mean ± SEM, n = 8) were analyzed by flow cytometry.