CD79, the signaling component of the B-cell receptor (BCR), is a promising target of antibodies and ADCs for the treatment of B-cell malignancies and autoimmune diseases. CD79 is a heterodimer, consisting of CD79a and CD79b, and is an attractive target because it is B cell specific and is expressed in almost all forms of non-Hodgkin's lymphoma and most forms of chronic lymphocytic leukemia. CD79 is particularly attractive for use as an ADC because the receptor is trafficked to a lysosome-like compartment as part of antigen presentation, thereby providing a mechanism for enhancing the release of drug from the ADC.