opsonisera

Opsonisera, in immunology, refers to the process of coating a pathogen or particle with molecules that promote its recognition and ingestion by phagocytes. The verb “opsonize” describes this action. Opsonization enhances phagocytosis and microbicidal activity and is a key step in the innate and adaptive immune response.

Opsonins include antibodies, particularly IgG, and complement fragments such as C3b and C4b. Immunoglobulins mark pathogens and engage Fc receptors on phagocytes, while complement fragments bind to complement receptors. Other molecules, such as C-reactive protein and mannose-binding lectin, can also function as opsonins by linking microbes to phagocytes or by promoting complement activation that deposits opsonins on the surface.

Phagocytes recognize opsonized targets through specific receptors, notably Fc gamma receptors for antibodies and complement receptors (for example CR1 and CR3) for complement fragments. This dual engagement increases the efficiency of engulfment and can trigger additional antimicrobial responses, including the respiratory burst and intracellular killing.

Clinical relevance includes the role of opsonization in protection against extracellular bacteria, especially encapsulated organisms like Streptococcus pneumoniae and Haemophilus influenzae. Deficiencies in antibodies, complement components (such as C3), or receptors can impair opsonization and raise susceptibility to infections. Vaccines often work in part by enhancing opsonizing antibody responses. Some pathogens counteract opsonization by expressing capsules or other surface features that limit opsonin binding.

In laboratory and clinical contexts, opsonization can be assessed by opsonophagocytic assays, which measure the capacity of serum or immune components to promote phagocytosis and killing of target bacteria.