ABSTRACT
The majority of cell types involved in the immune system are produced from a common hemopoietic stem cell (HSC) and develop through the process of differentiation into functionally mature blood cells of different lineages, for example monocytes, platelets, lymphocytes, and so forth (hemopoiesis: Figure 1). These stem cells are replicating self-renewing cells, which in early embryonic life are found in the yolk sac and then in the fetal liver, spleen, and bone marrow. After birth, the bone marrow contains the HSCs.
