CD20 is a transmembrane protein of the tetra-spanin family expressed on the surface of B-cells from peripheral blood as well as lymphoid tissues. CD20 expression persists from the early pre-B cell stage until the plasma cell differentiation stage. In addition to expression in normal B-cells, CD20 is expressed in B-cell derived malignancies such as non-Hodgkin's lymphoma (NHL) and B-cell chronic lymphocytic leukemia (CLL). The present invention includes anti-CD20 antibodies and antigen-binding fragments thereof comprising a light chain variable region and a heavy chain variable region, wherein the CDR-L1, CDR-L2, and CDR-L3 of said light chain variable region comprise the amino acid sequences of SEQ ID NOs: 17-19, respectively, and wherein the CDR-H1, CDR-H2, and CDR-H3 of said heavy chain variable region comprise the amino acid sequences of SEQ ID NOs: 20-22, respectively.
