Natural sCD100 released from activated T cells retains activities to enhance B-cell response.

(A) SDS-PAGE analysis of natural sCD100 purified from culture supernatants of ConA-stimulated 2B4 cells. 2B4 cells were stimulated with ConA (4 μg/mL) for 24 hours, and the resulting culture supernatants were harvested and passed through the affinity column to which anti-CD100 mAbs (BMA-12) were covalently bound. The bound protein eluted from the column was subjected to SDS-PAGE in reducing conditions and visualized by silver staining. Mr markers are indicated on the right. (B) The enhancing effect of sCD100 on B-cell proliferation. Small resting B-cells purified from C57BL/6 mice were cultured with or without anti-CD40 mAb (1 μg/mL), IL-4 (10 U/mL), CD100-Fc (20 μg/mL), or sCD100 (5 μg/mL) as indicated, for 3 days. Cells were pulsed with 2 μCi of [³H]-thymidine for the last 16 hours.