First, Ap1-17 reacted almost exclusively with sera from patients in the ACA+ group (all identified on a routine basis with anti-CENP-B ELISA), efficiently discriminating this group from the ACA− control groups, and reproducing the high concordance rate (94.3%) of sera reactivity to either CENP-A (Ap1-17 in our study) or CENP-B previously reported in a larger cohort of ACA+ SSc patients [26]. This evidence concerns the gene CENPB and systemic sclerosis.