Abstract: Provided herein are antibodies having the same epitope specificity as an antibody produced by the hybridoma cell line deposited with the American Type Culture Collection as hybridoma 4-2A6, 1-5A3, or 1-3B4. Further provided herein are methods of identifying and selecting cells that express FcRH1 or FcRH4. Methods of diagnosing and treating a subject with a malignancy of a hematopoietic cell lineage or an autoimmune disease and methods of modulating a humoral immune response in a subject are also provided herein. Further provided herein are polypeptides comprising one or more complementary determining regions of the disclosed antibodies and nucleic acids that encode the disclosed polypeptides.