On occasion, leukemia or lymphoma is discovered in abnormal results of routine blood tests. For example, above-normal white blood cell counts (leukocytosis) can be caused by immune cancers. Other immune cancers are diagnosed by abnormally high levels of antibodies in the blood. The antibody is usually of just one type, indicating that a single cell is dividing uncontrollably and secreting this antibody. What type of immune cell is the likely source of this antibody