TNFRSF17 and systemic lupus erythematosus: Our data reveal significantly increased BCMA expression levels on all investigated B cell subsets in SLE, which strongly correlated with serum anti-dsDNA antibody levels and the frequency of circulating plasmablasts, with the latter also correlating with soluble BCMA, identifying these markers as surrogates for disease activity as well as biomarkers for humoral activity in SLE.