PDGFRB and scleroderma: We found that PDGFR on spindle-like cells is highly phosphorylated in scleroderma skin, in sharp contrast to normal skin where PDGFR and phospho-PDGFR are virtually undetectable (mean ± SEM: 0.89 ± 0.02 and 0.93 ± 0.02 for phospho-PDGFRα/PDGFRα and phospho-PDGFRβ/PDGFRβ, respectively).