Affinity ligands and methods relating thereto

An affinity ligand that binds specifically to a target molecule, wherein the specific binding strength of the affinity ligand to the target molecule is reduced under buffer conditions comprising (i) a pH of 4.0 to 5.5 or (ii) 1-2 M MgCl2, wherein the affinity ligand is an anti-IgM antibody comprising at least one of (i) or (ii) as follows:

• (i) heavy chain complementarity determining regions CDR1, CDR2, and CDR3 sequences selected from:
• SEQ ID NO:223, SEQ ID NO:231, and SEQ ID NO:239, respectively;
• or
• SEQ ID NO:224, SEQ ID NO:232, and SEQ ID NO:240, respectively;
• or
• SEQ ID NO:225, SEQ ID NO:233, and SEQ ID NO:241, respectively;
• or
• SEQ ID NO:226, SEQ ID NO:234, and SEQ ID NO:242, respectively;
• or
• SEQ ID NO:227, SEQ ID NO:235, and SEQ ID NO:243, respectively;
• or
• SEQ ID NO:228, SEQ ID NO:236, and SEQ ID NO:244, respectively;
• or
• SEQ ID NO:229, SEQ ID NO:237, and SEQ ID NO:245, respectively;
• SEQ ID NO:230, SEQ ID NO:238, and SEQ ID NO:246, respectively, or
• (ii) light chain complementarity determining regions CDR1, CDR2, and CDR3 sequences selected from:
• SEQ ID NO:247, SEQ ID NO:255, and SEQ ID NO:263, respectively;
• or
• SEQ ID NO:248, SEQ ID NO:256, and SEQ ID NO:264, respectively;
• or
• SEQ ID NO:249, SEQ ID NO:257, and SEQ ID NO:265, respectively;
• or
• SEQ ID NO:250, SEQ ID NO:258, and SEQ ID NO:266, respectively;
• or
• SEQ ID NO:251, SEQ ID NO:259, and SEQ ID NO:267, respectively;
• or
• SEQ ID NO:252, SEQ ID NO:260, and SEQ ID NO:268, respectively;
• or
• SEQ ID NO:253, SEQ ID NO:261, and SEQ ID NO:269, respectively;
• or
• SEQ ID NO:254, SEQ ID NO:262, and SEQ ID NO:270, respectively.