To determine whether natural-plasma-derived CXCL4 behaves similarly, we stimulated HD pDCs with SSc plasma that contained high levels (195,000 ± 72,106 pg ml−1) or with HD plasma that contained low levels of CXCL4 (134 pg ml−1 ± 35) (Fig. 7a). This evidence concerns the gene PF4 and systemic sclerosis.