Levels of full-length BLyS and ΔBLyS mRNA strongly correlated with each other (r = 0.703; P < 0.001) in the SLE cohort, and plasma BLyS levels also correlated significantly with levels of each BLyS isoform (r = 0.429, P < 0.001; and r = 0.290, P = 0.024, respectively). The gene discussed is TNFSF13B; the disease is systemic lupus erythematosus.