PECAM1 and systemic lupus erythematosus: The genes expressed with a high degree of concordance between SLE PC and bone marrow PC include ADA, BCL6, CD79, CR2, CD19, CD22, LCK, SYK, CAV1, EMP, MYC and S100A4. Genes whose expression was discordant between SLE PC and bone marrow PC include CXCR4, ITGA6, SDC1, CD63, FCγRT, STCH, CD38, TNFAIP1, MHC2TA and PECAM1. The genes with the most striking discordance between SLE PC and bone marrow are CXCR4, SDC1, CD63, ITGA6 and FCγRT. SLE PC had very low expression of these genes.