CXCL12 and systemic sclerosis: Interestingly, when the relationship between Tang cells and SDF-1α levels was examined in the SSc patient subgroups, a significant inverse correlation was found only in patients with DU (Spearman’s rho = -0.52, p = 0.03) and in those with late NVC pattern (Spearman’s rho = -0.74, p<0.0001).