<qa>  What is the most common form of leukemia in adults?Chronic lymphocytic leukemia CLL is the most common form of leukemia in adults. CLL is a cancer of the B-lymphocytes, which make antibodies that help protect the body against harmful foreign substances, such as bacteria and viruses. Similar to CLL, small lymphocytic lymphoma SLL is a less-common cancer of the B-lymphocytes. In SLL, the abnormal lymphocytes mainly affect the lymph nodes; in CLL, the abnormal lymphocytes mainly affect the blood and bone marrow. 