Polypeptides and antibodies derived from chronic lymphocytic leukemia cells and uses thereof

An isolated antibody, or antigen-binding fragment thereof, that binds to CD200, wherein the antibody or antigen-binding fragment comprises:

• (i) a light chain polypeptide comprising:
• a light chain CDR1 comprising the sequence set forth in residues 26-35 of SEQ ID NO:207;
• a light chain CDR2 comprising the sequence set forth in residues 51-57 of SEQ ID NO:207;
• and a light chain CDR3 comprising the sequence set forth in resides 90-98 of SEQ ID NO:207;
• and
• (ii) a heavy chain polypeptide comprising:
• a heavy chain CDR1 comprising the sequence set forth in SEQ ID NO:111;
• a heavy chain CDR2 comprising the sequence set forth in SEQ ID NO:118;
• and a heavy chain CDR3 comprising the sequence set forth in residues 100-112 of SEQ ID NO:201.

A fusion molecule comprising:

• a first portion that targets cells bearing the OX-2/CD200 antigen, wherein the first portion is an antibody, or antigen-binding fragment thereof, that binds to CD200, wherein the antibody or antigen-binding fragment comprises:
• (i) a light chain polypeptide comprising:
• a light chain CDR1 comprising the sequence set forth in residues 26-35 of SEQ ID NO:207;
• a light chain CDR2 comprising the sequence set forth in residues 51-57 of SEQ ID NO:207;
• and a light chain CDR3 comprising the sequence set forth in resides 90-98 of SEQ ID NO:207;
• and (ii) a heavy chain polypeptide comprising:
• a heavy chain CDR1 comprising the sequence set forth in SEQ ID NO:111;
• a heavy chain CDR2 comprising the sequence set forth in SEQ ID NO:118;
• and a heavy chain CDR3 comprising the sequence set forth in residues 100-112 of SEQ ID NO:201;
• and
• a second portion that promotes the death of cells, wherein the second portion is a cytotoxic compound selected from the group consisting of a cytotoxic drug, a bacterial toxin, a radioactive isotope, an immunoglobulin constant region having antibody-dependent cellular cytotoxicity (ADCC) activity, and an immunoglobulin constant region having complement-dependent cytotoxicity (CDC) activity.