embodiment stem cell specific bivalent antibodies of the invention are used to stimulate the growth of hematopoietic stem cells in vitro or in vivo in some cases stem cell antibodies are used to treat patients suffering from or at risk of developing anemia or low white blood count these patients may be suffering from cancer and may be simultaneously treated with a cancer cell antibody of the invention for inhibiting their cancer cell growth in another aspect antibodies and peptides of the invention are used for diagnosis contacting a patient 39 s cells with a cancer specific antibody and getting significant binding would indicate that the patient has cancer similarly contacting a patient 39 s cells with a stem specific antibody and getting significant binding would indicate that the patient does not have cancer and would further identify those cells as stem or progenitor cells a patient 39 s cells can be contacted by both types of antibodies in order to distinguish stem cells from cancer cells such diagnosis can be carried out in vitro or in vivo in vitro a tissue specimen blood sample or bodily fluid sample can be analyzed using cancer or stem specific antibodies in vivo imaging agents can be attached to the antibodies of the invention to enable identification of cancer or stem cells in a patient development of monoclonal antibodies 2d6c8 and 2d6c3 also referred to here as c3 and c8 that facilitate human stem.