PF4 and systemic sclerosis: Most importantly, the correlation between serum IFN-α and anti-CXCL4 antibody reactivity was higher in SSc patients with lung fibrosis as compared to those with no lung fibrosis (Spearman’s r = 0.62, p = 0.016, n = 12 versus Spearman’s r = 0.37, p = 0.05, n = 20, respectively).