The first indirect evidence of anti-PDGFR antibody pathogenicity was provided by a small study demonstrating that dermal fibroblasts isolated from SSc patients treated with the immunosuppressant rituximab displayed a downregulation of type-1 collagen expression and of the anti-PDGFR autoantibody-triggered intracellular signaling [99,104]. Here, PDGFRB is linked to systemic sclerosis.