Claim: Leukemia is able to affect humans.

Bone marrow is the flexible tissue in the interior of bones . In humans , red blood cells are produced by cores of bone marrow in the heads of long bones in a process known as hematopoiesis . On average , bone marrow constitutes 4 % of the total body mass of humans ; in an adult having 65 kilograms of mass -LRB- 143 lbs -RRB- , bone marrow typically accounts for approximately 2.6 kg . The hematopoietic component of bone marrow produces approximately 500 billion blood cells per day , which use the bone marrow vasculature as a conduit to the body 's systemic circulation . Bone marrow is also a key component of the lymphatic system , producing the lymphocytes that support the body 's immune system .   Bone marrow transplants can be conducted to treat severe diseases of the bone marrow , including certain forms of cancer such as leukemia . Additionally , bone marrow stem cells have been successfully transformed into functional neural cells , and can also potentially be used to treat illnesses such as inflammatory bowel disease .