Patent ID: 6875846

Claim:
An isolated polypeptide comprising: (a) an APRIL subunit selected from: (i) human APRIL (SEQ ID NO:2) or partial human APRIL having an amino acid terminus starting at any one of amino acids 105 to 135 of human APRIL (SEQ ID NO:2); (ii) an amino acid substitution variant of human APRIL (SEQ ID NO:2) or partial human APRIL having an amino acid terminus starting at any one of amino acids 105 to 135 of human APRIL (SEQ ID NO:2), wherein said variant and said APRIL or partial APRIL share at least 75% sequence similarity; or (iii) a splice variant of human APRIL (SEQ ID NO:2), said variant missing amino acids 113 to 128 of human APRIL (SEQ ID NO:2); (b) linked via a non-covalent interaction to a BAFF subunit selected from: (i) human BAFF (SEQ ID NO:6) or partial human BAFF having an amino acid terminus starting at any one of amino acids 134 to 164 of human BAFF (SEQ ID NO:6); (ii) an amino acid substitution variant of human BAFF (SEQ ID NO:6) or partial human BAFF having an amino acid terminus starting at any one of amino acids 134 to 164 of human BAFF (SEQ ID NO:6), wherein said variant and said BAFF or partial BAFF share at least 75% sequence similarity; or (iii) a splice variant of human BAFF (SEQ ID NO:6), said variant missing amino acids 142 to 160 of human BAFF (SEQ ID NO:6), wherein said polypeptide induces proliferation of B cells.