Autologous T cell activation by dendritic cells co-cultured with platelets. Untreated dendritic cells (DCs) or DCs co-cultured for 48 h with platelets (PLTs) either in the same well or in filter-separated compartments were co-cultured with autologous CD4+ T cells stained with carboxyfluorescein diacetate succinimidyl ester (CFSE). After 7 days of co-culture, T cell proliferation was determined by the percentage of CFSElow cells (B) and culture supernatants were recovered and analyzed for IL-2 and IL-4 content (C). (A) Represents typical FACS histograms of CFSE staining of untreated or IL-2+ PHA-stimulated CD4+ T cells. (B) Percentage of CFSElow T cells in co-culture with DCs was calculated according to the following formula described in the Methods section. (B, C) values are mean ± SD of three independent experiments, with each experiment assessed in duplicate. Asterisks indicates statistical significance between assay and untreated DCs at p < 0.05 (*) or < 0.005 (**) by Mann-Whitney U test.