The genes upregulated and differentially expressed by both SLE PC and tonsil PC include ATF6, ESR1, IRF4, XBP1, SSR3 and chaperones (DNAJB4, -5, -9 and DNAJC1), whereas the downregulated genes included SPIB, CD22, BLK and FYN for example, indicating that both share a more mature molecular phenotype than tonsil PB. Here, XBP1 is linked to systemic lupus erythematosus.