The present disclosure relates to Cell Death Inducing Molecule (“CDIM”) binding proteins and pharmaceutical compositions thereof. Particularly, the disclosure provides CDIM binding proteins that are useful in the selective depleting and killing of B cells, including neoplastic B cells as well as neoplastic cells that are not of B-cell origin that express CDIM-like antigens. In addition, the disclosure encompasses polynucleotides encoding the disclosed antigen binding proteins, and expression systems for producing the same. Further the present disclosure encompasses methods of treating patients with B cell proliferative- and mediated diseases by administering the CDIM binding proteins as well as diagnostic assays for identifying proteins that bind to CDIM. The disclosure further contemplates diagnostic assays for identifying patient populations that can be treated with the CDIM binding proteins.