Csf1^op/Csf1^op; TgC/+ fibroblasts secrete normal levels of CSF-1 and express significant levels of cell-surface CSF-1.

(A) CSF-1 concentrations in culture supernatants of skin fibroblasts from +/+ (a), +/Csf1^op (b),Csf1^op/Csf1^op (c), andCsf1^op/Csf1^op TgC/+ (d) mice, determined by a CSF-1 radioimmunoassay that detects biologically active CSF-1. Means ± SEM for triplicate cultures. (B) Expression of cell-surface CSF-1 by the same fibroblasts, detected by anti–CSF-1 antibody staining and FACS analysis. The expression of cell-surface CSF-1 by Csf1^op/Csf1^op; TgC/+fibroblasts was confirmed by its trypsin-mediated release and measurement by CSF-1 radioimmunoassay. By this technique, it was expressed at one third the level of cell-surface CSF-1 on+/Csf1^op fibroblasts (data not shown).