TOP1 and systemic sclerosis: Interestingly, stimulation with peptide 2, which corresponds to amino acid position 475-486 (RAVALYFIDKLA) of DNA topoisomerase-I protein, induced a higher percentage of IFN-γ secreting CD4+ T cells in SSc patients without anti-Scl-70 antibody than that observed in patients with anti-Scl-70 antibodies.