CLL is the most common type of Leukemia in adults. Chronic lymphocytic leukemia (CLL) is a form of blood cancer that affects a type of white blood cell (WBC) called a “lymphocyte.” Lymphocytes help our body in fighting infections. They’re made in the soft center of the bones, called the marrow. If you have CLL, your body makes an abnormally high number of lymphocytes which alter the normal functioning of the blood cells. CLL  however, usually grows slowly, so you may not have symptoms for years.