Although the associations between full-length BLyS and/or ΔBLyS mRNA levels and disease activity in SLE were usually strong when the SLE cohort was analyzed in aggregate, there were several SLE patients in whom BLyS mRNA levels were quite high despite little objective ongoing disease activity, and there were several SLE patients in whom BLyS mRNA levels were low despite considerable ongoing disease activity. This evidence concerns the gene TNFSF13B and systemic lupus erythematosus.