This finding was unexpected since membrane-bound APRIL is efficiently processed into its soluble form.[8], [32] Since the novel isoform APRIL-δ lacks the consensus motif required for furin convertase-mediated cleavage (Figure 2B) and contains a transmembrane-like domain, it is possible that the APRIL detected on the cell surface of B-ALL cells represents this isoform. Here, TNFSF13 is linked to acute lymphoblastic leukemia.