CD38 and rheumatoid arthritis: In this study, using integrative analysis of synovial tissue biopsies obtained from different stages of RA disease and PBMC, we have shown that 1) CD38 and plasma cell/plasmablast-related genes are up-regulated in ACPA+RF+ arthralgia and UA disease stages before the onset of RA; 2) CD38 is expressed at the highest level on plasma cells compared to other immune cell populations in RA, SLE and healthy donors in the peripheral blood; and most importantly 3) daratumumab effectively depletes plasma cells/plasmablast in SLE and RA PBMC ex vivo.