Lymphopoiesis is the process of creating lymphocytes, including B cells, T cells, and natural killer cells, in the bone marrow. The process involves differentiation of pluripotent hematopoietic stem cells into various progenitor cells, which can give rise to different types of lymphocytes. In T-cell lymphopoiesis, lymphocytes are formed in the bone marrow and mature in the thymus, while in B-cell lymphopoiesis, B lymphocytes are formed in the bone marrow and transported to the lymph nodes for antigen recognition and activation into plasma cells that secrete antibodies.
In immunology, white blood cells can be classified as polymorphonuclear neutrophils, polymorphonuclear basophils, polymorphonuclear eosinophils, monocytes, lymphocytes, or plasma cells. Lymphopoiesis is the process of making lymphocytes, such as B cells, T cells, and natural killer cells, in the bone marrow. In this process, progenitor cells in the bone marrow differentiate into lymphocytes. Lymphopoiesis is necessary for survival because mature lymphocytes are essential elements of the body’s lymphatic system.
The formal term for lymphopoiesis is lymphoid hematopoiesis, which basically means the production of blood cells called lymphocytes. Undifferentiated cells, called pluripotential hematopoietic stem cells, in the bone marrow can undergo a series of cell divisions and differentiations before engaging in the production of red blood cells, myelocytes, or lymphocytes. In lymphopoiesis, the pluripotent hematopoietic stem cell gives rise to the multipotent progenitor cell. This cell gives rise to the early lymphoid progenitor, which in turn gives rise to the common lymphoid progenitor (CLP). The common lymphoid progenitor can give rise to natural killer (NK) cells, dendritic cells, and prolymphocytes.
In T-cell lymphopoiesis, lymphocytes are first formed in the bone marrow and then transported to the thymic cortex where they undergo maturation. T cells in the thymus remain in an antigen-free environment for nearly 1 week. Only 2-4% of the original T cell population is able to survive in this environment.
Other T cells undergo apoptosis or are eaten and destroyed by macrophages. The death of this large number of T lymphocytes ensures that the surviving lymphocytes can recognize major histocompatibility complexes (MHC). Recognition of this complex prevents autoimmune destruction of body cells. T cells or thymocytes can differentiate into helper (Th) T cells, cytotoxic (Tc) T cells, memory T cells, and regulatory or suppressor T cells.
In B-cell lymphopoiesis, B lymphocytes are initially formed in the bone marrow. When the bone marrow is damaged, the spleen may take over this function. The first studies on B lymphocytes were done on the bursa of Fabricus present in chickens, which is why they are called B lymphocytes. After formation, the B cells are then transported to the lymph nodes and introduced into the antigens.
Antigen recognition is an important function of B cells. Once a B cell recognizes an antigen, it becomes activated and differentiates into the plasma cell, a cell that secretes antibodies. The antibodies bind the antigen and stimulate destructive mechanisms, such as the complement system and macrophage phagocytosis. The most common antibody secreted is immunoglobulin G (IgG). Other antibodies, such as immunoglobulin A (IgA), immunoglobulin E (IgE), and immunoglobulin M (IgM), can also be produced by mature B cells.
Protect your devices with Threat Protection by NordVPN
