A small portion of the intercellular tissue fluid that does not diffuse directly back into the bloodstream through the walls of the blood capillaries is taken up by lymphatic capillaries. It is eventually enriched with immune defense cells and peptides and polypeptides for immune control. This fluid is called lymph and it is the lymph formation.
What is lymph formation?
In humans, about 2 to 3 liters of lymph are produced per day. Lymph is enriched with lymphocytes in the lymphatic vessels. About 10% of the intercellular fluid that enters the intercellular space from the blood capillaries cannot diffuse back through the walls of the blood capillaries into the bloodstream. Usually, larger molecules from degradation products of the extracellular space or hydrophobic substances prevent the direct return to the blood circulation. This residual fluid is taken up by the open ends of the lymphatic capillaries, which extend into the intercellular space, and transported toward the lymph nodes. In humans, about 2 to 3 liters of lymph are produced per day. In the lymphatic vessels, the former tissue fluid, which contains ions and enzymes, among other things, is enriched with lymphocytes, i.e. white blood cells such as B and T lymphocytes and natural killer cells of the innate immune defense. In addition, depending on the need and stimulation, the immune cells secrete cytokines, which the immune system uses to control the immune response. The resulting former tissue fluid enriched with immune cells as well as cytokines and so-called lymphobligatory loads is called lymph. If the surrounding tissue is affected by pathogenic germs, the lymph may also contain corresponding germs or their degradation products, indicating an already successful defense by tissue macrophages. Similarly, in certain tumor diseases, metastatic cancer cells may be washed from the tissue fluid into the lymphatic vessels.
Function and role
Decentralized “on-site” lymphatic formation has the major advantage that immune responses to specific challenges can be not only global throughout the body’s circulation but also localized. Immune responses to inflammatory sites can be directly controlled by lymph formation. Continuous lymph formation stimulates open lymphatic circulation. The lymph vessels are given a stimulus to carry the lymph further at regular intervals with peristalsis-like contractions. Lymph formation in the digestive tract is different from lymph formation in the rest of the body. Lipid substances and proteins that cannot enter the blood directly through the capillary walls in the intestinal walls due to their molecular size are washed into the open lymphatic capillaries. The substances are accepted by the lymphatic system after “input control” and are transported further with the lymph in order to finally enter the bloodstream via one of the vein angles below the heart after all. If the immune system detects harmful substances or pathogenic germs during the entry control of the large-molecule lipids or proteins, an immediate immune response takes place via the control of lymph formation. Without the lymph formation, a congestion of cellular degradation products in the intercellular space and unrestrained multiplication of pathogenic germs would occur very soon, because an individual immune response to local processes in the tissue would not be possible. The removal of dead and decomposed endogenous cells would also not be possible, resulting in the formation of toxic substances and poisoning of the tissue. The decentralized formation of lymph is essential for the body’s immune responses and metabolism.
Diseases and ailments
One of the most common complaints and disorders associated with lymph formation is not related to functional impairment of lymph formation or the nature of lymph, but is due to functional impairment of the lymphatics. Lymphatic drainage may be so impaired due to obstruction of the lymphatic pathways that accumulations of lymph in the tissues occur, known as lymphedema. The most common cause for the occurrence of lymphedema in the lymphatic vessels and intercellular space is postoperative symptoms following surgical removal of surrounding lymph nodes for prevention or elimination of already metastasized tumor cells that have become lodged in the lymph nodes.A parasitic disease that results in extreme lymphatic congestion in the lower extremities down to the knees and in the external genital organs is elephantiasis, which in the tropical highlands is usually caused by worm parasites. Other causes of lymphatic congestion may be a rare bacterial inflammation of the lymphatics (lymphangitis) or lymph nodes (lymphadenitis). Chemotherapy and radiation therapy, as unavoidable side effects, can also impair the function of the lymphatics and lymph nodes, causing lymphedema to develop. Further impairment of the lymphatic system can be caused by malignant lymphoma. This is a type of cancer that affects the primary organs of the lymphatic system, but especially the lymph nodes. A distinction is made between Hodgkin’s lymphoma and non-Hodgkin’s lymphoma. The distinction between the two types of cancer is based solely on whether Sternberg-Reed cells can be detected in the tumor. If this is the case, the tumor is Hodgkin’s lymphoma. “Sternberg-Reed giant cells,” as they are also called, result from mergers and fusions of multiple B lymphocytes originating from the germinal center of lymph nodes. One disease that directly affects lymph formation is chronic lymphocytic leukemia (CLL). In simple terms, there is an excessive proliferation of leukocytes. CLL is the most common leukemia in the industrialized world, accounting for approximately 33% of all leukemias. In the course of the disease, an increased number of non-functional leukocytes are formed, leading to swelling of the liver and spleen, as well as displacement of the precursor cells for red blood cells in the bone marrow. In advanced disease, life-threatening anemia sets in.
