To determine whether c-FOS mediated the effect of SSc-IgG on the IL-6 promoter, an electrophoretic mobility shift assay (EMSA) was performed using a biotin-labeled consensus oligonucleotide for c-FOS binding that corresponded to positions −278 to −257 of the IL-6 promoter (Figure 6B). This evidence concerns the gene IL6 and systemic sclerosis.