Figure 4.

Phosphorylated platelet-derived growth factor receptor expression in the rituximab treated systemic sclerosis patients. Substantial reduction of collagen accumulation following rituximab (RTX) treatment (B) compared with baseline (A) in Patient 2 (Masson's trichrome ×100). Immunohistochemical staining for phosphorylated platelet-derived growth factor receptor (PDGFR)α and PDGFRβ in the same patient prior to ((C) and (E), respectively) and following ((D) and (F), respectively) RTX treatment, where a significant decrease in phospho-PDGFR staining can be seen (streptavidin peroxidase ×100). Red arrow in the boxed area points to a spindle-like cell (among others) expressing phosphorylated PDGFRα and PDGFRβ.