Binding activity and antigen-presenting capacity of DCs from CD18^−/− mice. (A) Wells of a 96-well plate were coated with 10 μg/mL of either recombinant ICAM-1–Fc (top panel), recombinant P-selectin–Fc (bottom panel), or human IgG (▪). Then 1 × 10⁶ T cells/well or 5 × 10⁵ bmDCs (CD18^+/+, □; CD18^−/−, ⊡) were left unstimulated or treated with PMA/ionomycin (3 ng/300 ng/mL), LPS (100 ng/mL), or CD40L (1 μg/mL), and were incubated for 45 minutes at 37°C. Wells were washed 4 times and assessed for bound cells by digital microscopy. (B) bmDCs (5 × 10⁴) of either CD18^+/+ or CD18^−/− mice were incubated with 5 × 10⁵ CD18^+/+ T cells in a collagen gel. Contacts of T cells and bmDCs were recorded by video microscopy and individual DC–T-cell pairs were analyzed for their contact times. Data are representative of 3 separate experiments ± SEM. (C) BALB/C T cells (2 × 10⁵) were incubated with allogeneic bone marrow DCs of either CD18^−/− or CD18^+/+ mice for 3 days and pulsed for 18 hours with 1 μCi (0.037 MBq) ³H-thymidine before ³H-thymidine incorporation was assessed. Data are representative of 3 independent experiments. (D) Supernatants of panel C were measured for cytokine content using CBA and analyzed by flow cytometry. Data are expressed as means of 3 independent experiments.