Among the class-switched B-cell clusters, we could see a significant difference (p = 0.01) in an IgG+CD27+CD24+CD43+ B-cell sub-population with lower cells numbers in both ACPA− and ACPA+ RA (cluster 30, Fig. 2, Supplemental Figs. 4 and 5, Table 1). Here, SPN is linked to rheumatoid arthritis.