DC-SIGN is partially implicated in IVIg-mediated COX-2 expression and PGE₂production in DCs and Treg expansion. (A) Expression of DC-SIGN in DCs as analyzed by flow cytometry. (B) Western-blot analysis of COX-2 expression in DCs. DCs were cultured in GM-CSF and IL-4 alone (Ctr) or with IVIg or HSA for 24 hours. In parallel, DCs were preincubated with blocking antibodies to DC-SIGN followed by treatment with IVIg (Anti-DC-SIGN+IVIg). Representative blot of 6 experiments is shown. (C) The fold changes in the COX-2 expression based on densitometry analysis of western blots (mean ± SEM, n = 6). AU, arbitrary units. (D) Secretion (mean ± SEM, n = 6) of PGE₂ by DCs that were treated as explained above. (E) Percentage (mean ± SEM, n = 7) of CD4⁺CD25⁺FoxP3⁺ cells in the DC-CD4⁺ T cell cocultures. DCs were pretreated with DC-SIGN blocking antibodies or isotype control antibodies followed by treatment with IVIg and then cocultured with CD4⁺ T cells, *P < .05; **P < .01; ***P < .001.