Expression of SCF isoforms in stromal cell transfectants.

(A) Stromal cells expressing soluble, MA, and MR forms of SCF were lysed and an equal amount of protein was subjected to Western blot analysis using an anti-SCF antibody. A 38-kilodalton (kD) SCF band can be seen in stromal cells expressing the soluble (lane 1), MR (lane 2), and MA (lane 3) forms of SCF. (B) Quantitation of secreted SCF in conditioned medium from stromal cells expressing S-SCF. Lane 1: concentrated conditioned medium from S-SCF–producing stromal cells. Lanes 2, 3, and 4: 6, 3, and 1 ng recombinant E coli–derived SCF (15 kD), respectively. Shown is a Western blot probed with an anti-SCF antibody. Molecular weight of stromal cell secreted soluble SCF (38 kD) and E coli–derived SCF (15 kD) protein is indicated.