The present invention relates to modified antigen binding molecules (ABMs). In particular embodiments, the present invention relates to recombinant monoclonal antibodies or fragments, including chimeric, primatized or humanized antibodies or fragments, having altered ability to mediate cell signaling activity by a target antigen, and/or altered ability to mediate cross-linking of one or more target antigens. In addition, the present invention relates to nucleic acid molecules encoding such modified ABMs, and vectors and host cells comprising such nucleic acid molecules. The invention further relates to methods for producing the modified ABMs of the invention, and to methods of using these modified ABMs in treatment of disease. In addition, the present invention relates to modified ABMs with modified glycosylation having improved therapeutic properties, including antibodies with increased Fc receptor binding and increased effector function.