Opsonisoivien

Opsonisoivien is a term used in immunology to refer to factors that promote opsonization, the process by which pathogens are marked for destruction by phagocytes. In this context, an opsonisoiva agent is any molecule that enhances the recognition and uptake of microbes by immune cells such as neutrophils and macrophages.

Opsonization works by coating the surface of a pathogen with specific molecules that are recognized by phagocyte receptors. The main opsonins are antibodies, particularly IgG and IgM, and complement fragments such as C3b and its inactivated form iC3b. These opsonins bind to microbial surfaces and present binding sites for receptors on phagocytes, including Fc receptors for IgG and complement receptors like CR1 and CR3. Other soluble proteins, such as collectins (for example mannose-binding lectin), can also function as opsonins by binding to carbohydrate patterns on pathogens and bridging them to phagocytes.

There are two principal pathways that lead to opsonization: the classical pathway, which is antibody-dependent, and the alternative pathway, which can deposit opsonins like C3b directly onto targets without antibodies. The result of opsonization is enhanced phagocytosis and often an increased respiratory burst and microbial killing.

Clinical relevance is significant: deficiencies in opsonins or their receptors can lead to increased susceptibility to infections, particularly with encapsulated bacteria. Vaccination and therapeutic antibodies aim to enhance opsonization, illustrating the practical importance of opsonisoivien in host defense.