[13] Opsonins and dysopsonins: An overview

Publisher Summary This chapter provides an overview of opsonins and dysopsonins. “Phagocytosis” refers to the process by which a particle is recognized by the phagocyte as being foreign and is ingested by the cell and subsequently sequestered in an intracellular vacuole. This process is initiated by the migration (chemotaxis) of the phagocyte to the site of microbial infiltration. Once contact between the particle and granulocyte has been achieved, a cohesive force prevents their separation despite extracellular fluid flow. This critical step in the phagocytic process is known as the “adhesive phase.” The prerequisite for ingestion and subsequent digestion is the formation of the critical adhesive bond between the particle to be ingested and the phagocytic cell. Several biological entities are known to either promote (opsonins) or retard (dysopsonins) this event. Opsonins (and dysopsonins) primarily affect the critical first step in phagocytosis—that is, the attachment phase between the phagocyte and the particle. The heat-stable opsonins that appear in the serum of immunized animals are specific for the immunizing agent and are adsorbed from the serum by the strain used for immunization but not by other organisms.