Type 1 cells are distinguished by the incapacity of anti-apoptotic members of the Bcl-2 family (namely Bcl-2 and Bcl-xL) to defend against Fas-mediated apoptosis. Type 1 cells that have been identified include H9, CH1, SKW6.4, and SW480, all of which are lymphocyte lineages with the exception of SW480, which is a colon adenocarcinoma lineage. Type 2 cells express high levels of Bcl-2 or other inhibitors of apoptosis and are resistant to Fas-induced death.
Type 1 cells die through an active process called "fratricide" when they recognize their homologous receptor on neighboring cells. This form of cell suicide is important in immune responses because it prevents the survival of abnormal or infected cells. In contrast, type 2 cells die through a passive process called "phagocytosis" when they are ingested by another cell.
Fas is expressed on nearly all nucleated cells and provides a "death signal" when its ligand is present on another cell. Binding of this ligand to Fas triggers a signaling cascade within the receiving cell that results in its own demise. Mutations or deletions of Fas or its ligand can cause hyper-responsive or hypo-responsive types of autoimmune disease, respectively.
The fact that different types of cells die through distinct mechanisms may explain why mutations in Fas or its ligand can have such diverse effects. It also suggests that therapies designed to inhibit apoptosis might not be effective for all diseases associated with defects in apoptosis regulation.
According to the Mayo Clinic, these tiny white blood cells serve an important role in disease defense. B-cells, which produce antibodies that combat bacteria and poisons, and T-cells, which aid in the destruction of diseased or malignant cells, are the two kinds of lymphocytes. Lymphocytes are the body's first line of defense against viruses and bacteria that enter through the skin or airways. The immune system also includes neutrophils, eosinophils, basophils, mast cells, dendritic cells, and natural killer cells.
B-cells are special type of cell that develops from bone marrow cells. When they divide, their daughter cells will usually become one of two types: plasma cells, which make antibodies, or memory cells. Only plasma cells can reproduce rapidly; they're called blast cells because they make many new proteins at once, so they can react quickly to an attack on the body. Memory cells don't divide but they do create more B-cells if needed. Plasma cells and memory cells work together to provide a quick response to future attacks by producing specific antibodies.
T-cells are special type of cell that helps B-cells perform their job. T-cells can be divided into several categories based on how they recognize an antigen (i.e., a foreign molecule).
FAS is an abbreviation for Famili (Fas cell surface death receptor)
|Entity||Autoimmune lymphoproliferative syndrome type Ia|
FAS (Fas Cell Surface Death Receptor) is a gene that codes for a protein. Autoimmune Lymphoproliferative Syndrome and Lymphoproliferative Syndrome are two diseases related with FAS. Allograft rejection and PEDF-induced signaling are two of its linked mechanisms. Fas/Fas ligand plays an important role in regulating the immune system.
FAS was first identified by Drs. Shuzo Yoshida and Hiroshi Murakami at the Tokyo University Medical School. They named it after the Fas antigen, which is one of several proteins that transmit signals from cell surfaces to the body's immune system. The Fas antigen belongs to a family of cellular receptors that regulate the survival of cells themselves as well as other cells. When activated, Fas kills cells by triggering an immune response similar to that initiated by CD40. Mutations in this gene cause autoimmune lymphoproliferative syndrome (ALPS), which is characterized by abnormal T-cell proliferation leading to organ damage due to inflammation. ALPS patients develop severe autoimmune disorders such as diabetes, arthritis, and thyroiditis. Some patients also have neurological problems such as dementia and nerve damage.
FAS is expressed on many types of cells including T-cells, B-cells, macrophages, dendritic cells, endothelial cells, fibroblasts, and neurons.