When bone marrow develops, it eventually assumes the task of forming most of the blood cells for the entire organism.
[3] However, maturation, activation, and some proliferation of lymphoid cells occurs in the spleen, thymus, and lymph nodes.
[3] In a healthy adult person, approximately 1011–1012 new blood cells are produced daily in order to maintain steady state levels in the peripheral circulation.
[11] Haematopoietic stem cell transplantation remains a dangerous procedure with many possible complications; it is reserved for patients with life-threatening diseases.
As survival following the procedure has increased, its use has expanded beyond cancer to autoimmune diseases[13][14] and hereditary skeletal dysplasias; notably malignant infantile osteopetrosis[15][16] and mucopolysaccharidosis.