Opsoniner

Opsoniner is a term that is not widely used in standard immunology, but when encountered it generally refers to a molecule, particle, or therapeutic agent that mediates opsonization—the process by which a pathogen or particle is marked for ingestion by phagocytes. In most current literature, the functions described under this concept are attributed to known opsonins, such as antibodies and complement fragments; thus, “opsoniner” is often treated as synonymous with an opsonizing agent or an opsonizing activity of a substance.

Mechanism and role

An opsoniner would bind to the surface of a microorganism or debris and simultaneously present a binding site recognizable by phagocyte receptors. This dual interaction lowers the threshold for phagocytosis, promoting attachment, engulfment, and subsequent destruction of the target by cells such as neutrophils and macrophages. The effectiveness of opsonization depends on the compatibility of the opsoniner with phagocyte receptors, including Fc receptors for antibody Fc regions and complement receptors for complement fragments.

Examples and context

Physiological examples of opsonizing activities include IgG antibodies and C3b deposited from the complement system, which tag pathogens for phagocytosis. Collectins and other innate immune proteins can also function to mark targets. Therapeutically, monoclonal antibodies or intravenous immunoglobulin (IVIG) preparations can serve an opsonizing role by enhancing uptake of pathogens or diseased cells. Clinically, defects in opsonization pathways or receptor function can lead to increased susceptibility to infections, particularly with encapsulated bacteria.

Note

The preferred and widely accepted terms remain “opsonin” and “opsonization.” The label “opsoniner” is collateral terminology and may be encountered in some texts as a descriptive or informal expression for an opsonizing agent.