FIG. 1.

DC secrete CTLA-4. (A) Human DC were differentiated (GM-CSF, IL-4) from the adherent fraction of a buffy coat with or without prior CD14 selection and CD11c enrichment and subsequently matured with IL-1β, IL-6, TNF-α, and PGE₂ for 48 h. DC were also treated with either NT siRNA or CTLA-4 siRNA at the time of maturation, and DC-cultured supernatants were collected and assayed for CTLA-4 compared to variously stimulated nonadherent PBMC derived from the same buffy coat. (B) DC-cultured supernatants were rotated overnight at 4°C with protein G-plus beads coated with either the BNI3 clone or A3.6B10.G1 clone of αCTLA-4, or an isotype control antibody. IL-12p35 was used to validate antibody coIP specificity. CTLA-4, cytotoxic T-lymphocyte-associated protein-4; DC, dendritic cells; GM-CSF, granulocyte-macrophage colony-stimulating factor; NT, nontargeting; PBMC, peripheral blood mononuclear cells.