The invention relates to antibodies directed to a2ß1 integrin and their uses, including humanized anti-alpha 2 (a2) integrin antibodies and methods of treatment with anti-a2integrin antibodies. More specifically the present invention relates to humanized anti-a2 integrin antibodies comprising a heavy chain variable region, a light chain variable region, a human light chain constant region and a variant human IgG1 heavy chain constant region which exhibit altered effector function.
