Nucleated cells and colony-forming cell expansions in cocultures of CD34⁺ progenitors with HUVEC stimulated by CD40L.

CD34⁺ progenitors (20 000) isolated from cord blood were cultured with 10% supernatant of nontransfected COS cells (control), with 10% supernatant of CD40L-CD8α–transfected COS cells (CD40L) in the absence or presence of anti-CD40 mAb at 5 μg/mL (CD40L + aCD40). Half of the medium was exchanged at day 6 with readdition or not of the antibody. At day 12, the expansion of the nucleated and of clonogenic cells was measured and cells plated for clonogenic assays. A and B: noncontact coculture. C and D: contact coculture. Results are expressed as the mean ± SD–fold cell expansion (A, C) or colony number (B, D) (for 10⁵ cells), for 6 experiments (values significant for CD40L versus control [*] and CD40L + aCD40 versus CD40L [**]).