ALCAM is expressed by monocyte-derived DCs and mediates adhesion to CD6. (A) Characterization of mature DCs. DCs were stained with mAbs against costimulatory molecules and DC-specific molecules. Empty histograms represent isotype-matched controls; shaded histograms, antibody staining. Percentage of positive cells and mean fluorescence intensity (MFI) values are indicated in the top right corner of each subpanel. (B) ALCAM expression is not altered upon maturation of DCs. Immature DCs (left) were stimulated with LPS (2 μg/mL) for 2 days to obtain mature DCs (right). Open histograms represent isotype-matched controls; shaded histograms, antibody staining. Percentage of positive cells and MFI values are indicated in the top right corner of each subpanel. (C) DCs adhere to CD6-Fc–coated microbeads. Immature DCs, mature DCs, and control myelomonocytic KG1a cells were allowed to adhere to CD6-Fc–coated fluorescent beads after preincubation with or without mAb J4-81 (anti-ALCAM) for 45 minutes at 37°C and were analyzed by flow cytometry. ALCAM-specific adhesion is expressed as the adhesion percentage after subtraction of adhesion in the presence of mAb J4-81. One representative experiment of 3 is shown.