Abstract: The present invention provides compositions and methods for increasing the amount of active Syk protein kinase and or SHP-1 protein phosphatase in a cell. The compositions and methods are useful for increasing the efficacy of anti-neoplastic agents, such as those that target the CD33 protein, and which are used to treat leukemia. The invention thus provides for treatment of cancers, including leukemias. The invention also provides screening assays for anti-neoplastic agents in vitro. Methods of screening patients for responsiveness to anti-CD33 treatments are also provided.

Abstract: Disclosed herein are hybridomas, antibodies produced thereby, antigens, and cells identified or isolated therewith. The dendritic like cells preferably have dendritic morphology and B cell phenotype. Methods of utilizing the hybridomas, antibodies, antigens, and cells are also discussed herein.

Abstract: Bispecific molecules comprising a target cell specific ligand and an effector cell specific antibody or functional antibody fragment are disclosed.

Abstract: Bispecific molecules which react both with the high-affinity Fc.gamma. receptor of human effector cells and with a target cell surface antigen are disclosed. Binding of the molecules to the Fc receptors found on effector cells is not blocked by human immunoglobulin G. The molecules are useful for targeting human effector cells (e.g. macrophages) against cells bearing the target antigen. For this purpose, bispecific molecules can be constructed containing the binding region derived from an anti-Fc.gamma. receptor antibody and the binding region derived from an antibody specific for the target antigen. Targeted effector cells can be used to destroy cells bearing the target cell surface antigen by cell-mediated antibody dependent cytolysis and by complement-fixation.

Abstract: Bispecific molecules comprising a non-immunoglobulin tumor cell specific ligand and an antibody which binds the Fc receptor of an effector cell at a site that is not inhibited by endogenous immunoglobulin are disclosed. The bispecific molecules can be used to induce a specific antibody dependent effector cell-mediated cytotoxicity against tumor cells, such as small cell lung carcinoma (SCLC) cells, either in vivo or in vitro.