Humanized L243 antibodies

A humanized L243 antibody or antigen-binding fragment thereof, comprising heavy chain variable domain complementarity determining region (CDR) sequences CDR1 (NYGMN, residues 31 to 35of SEQ ID NO:

• 4), CDR2 (WINTYTREPTYADDFKG, residues 50 to 66 of SEQ ID NO:4), and CDR3 (DITAVVPTGFDY, residues 99 to 110 of SEQ ID NO:4) and heavy chain framework residues F27, K38, K46, A68, and F91 and light chain variable domain CDR sequences CDR1 (RASENIYSNLA, residues 24 to 34 of SEQ ID NO:2), CDR2 (AASNLAD, residues 50 to 56 of SEQ ID NO:2), and CDR3 (OHFWTTPWA, residues 89 to 98 of SEQ ID NO:2) and light chain framework residues R37 , K39 , V48 and F49, wherein the remainder of the humanized L243 antibody framework region and constant region sequences are from one or more human antibodies, wherein the humanized L243 antibody has the ability to bind to HLA-DR on HLA-DR+ cells, and wherein said humanized L243 antibody induces apoptosis of said HLA-DR+ cells without inducing complement-mediated cytotoxicity (CDC) or antibody-dependent cell mediated cytotoxicity (ADCC).