Final answer:
Pro-B cells are derived from pluripotent hematopoietic stem cells in the bone marrow and go through a process called hematopoiesis. These cells are a crucial stage in the development of B cells, which are a part of the immune system. The liver and spleen can also produce blood cells through extramedullary hematopoiesis when the bone marrow is unable to do so.
Step-by-step explanation:
Pro-B cells develop from pluripotent hematopoietic stem cells (HSCs) within the bone marrow. These stem cells have the remarkable potential to differentiate into any type of human tissue, including all the formed elements of blood, such as red blood cells, platelets, and immune cells like B and T cells. The process of differentiation from HSCs to mature blood cells is known as hematopoiesis.
During hematopoiesis, pluripotent stem cells progress through various intermediate stages, including precursor cells identified by names ending with the suffix '-blast'. For example, lymphoid precursor cells will eventually develop into lymphocytes, which include B cells. Pro-B cells are an early stage in B cell development and continue to mature in the bone marrow until they are ready to play their role in the body's immune response.
In scenarios where bone marrow functionality is compromised, such as in bone cancer, the liver and spleen can undertake extramedullary hematopoiesis to continue producing the necessary blood components.