Mannose-binding lectin (MBL) is a protein produced by the liver that plays a crucial role in the immune system. It recognizes and binds to specific sugars found on the surface of certain pathogens, such as bacteria and viruses. This binding helps to activate the complement system, a part of the immune response that enhances the ability to clear infections. MBL is important for the body's defense against infections, especially in individuals with weakened immune systems. Deficiencies in MBL can lead to an increased susceptibility to infections, highlighting its significance in maintaining overall health and immunity.