Surface antigens are proteins on cell membranes that signal various biological processes. They can be used to detect diseases or organ transplant rejection. HBV antigens are released by viruses and can be used to diagnose disease. Different types of antigens can be found on immune cells and act as markers for different functions. Antigen tests can diagnose some diseases.
A surface antigen is a type of protein on a cell membrane that can signal various biological processes, including immune reactions. There are various antigens which often include receptors, adhesion molecules and enzymes. Some varieties are released into the environment between cells and, depending on the type of protein, certain diseases or the rejection of an organ transplant can be detected. Surface antigens are often released by viruses such as hepatitis B (HBV). Able to signal viruses to replicate, these compounds in a blood sample are typically used to diagnose disease.
HBV antigens are usually released by replicating viruses in the liver and then the excess proteins join in the blood. A laboratory test can identify surface antigen in a sample. One type associated with HBV is usually found in liver cells, while others can be detected in the bloodstream. If the virus is found together with the antibodies, this usually means that the immune system is trying to fight the infection. A negative test for antibodies generally means there is no immune response to the virus.
In general, the type of surface antigen present helps determine the type of immune cells most prevalent, as well as the stage in their life cycle. Different types of antigens can be found on the surface of an immune cell called a lymphocyte. Because they are often used to help identify the cell, antigen markers are also called clusters of differentiation (CD). The different types of antigens on a cell surface can include an adhesion molecule called immunoglobulin and integrin Beta 2 which is associated with lymphocyte function. Others include antigens such as selectin and cadherin.
Some CD antigens act as markers for helper and suppressor cells in the immune system. Viruses can latch onto some to trigger an infection, such as when human immunodeficiency virus (HIV) binds to the receptor to enter a cell. Another type of surface antigen serves as a marker for stem cells, or those that can be activated and formed in any other tissue in the body.
There are many surface antigen proteins that transmit signals across the cell membrane. These signals can be sent if an immune cell is activated and is communicating to others to respond. Researchers generally know which antigens are related to which cell types, as well as those associated with particular diseases. An antigen test is often sufficient to diagnose some diseases.
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