SLAM-expressing CD40L-L cells induce phenotypic maturation of DCs. (A) Cell-surface expression of SLAM on CD40L-L cells stably transfected with SLAM was measured by flow cytometry. SLAM expression on the surface of a polyclonal population of FACS-sorted stable transfectants (top histogram) and a representative SLAM/CD40L-L cell clone obtained by limiting dilution is shown (bottom histogram). (B) Expression of SLAM on untreated human peripheral-blood T lymphocytes (top histogram) or following activation with 5 μg/mL anti-CD3 mAb (OKT3) for 24 hours (bottom histogram). (C) Expression of SLAM molecules on the surface of monocyte-derived DCs without activation (top histogram), following a 24-hour activation with the indicated inflammatory cytokines (middle histogram), or with CD40L-L cells for 24 hours (bottom histogram). Dashed lines represent staining with isotype control antibodies. Typical results of 4 donors analyzed in independent experiments are shown.