Opsonin
（重定向自Opsonization）
![Action of opsonins: a phagocytic cell recognises the opsonin on the surface of an antigen](/Images/godic/202501/31/Opsonin3352.png")
An opsonin (from the Greek opsōneîn, to prepare for eating) is any molecule that enhances phagocytosis by marking an antigen for an immune response or marking dead cells for recycling (i.e., causes the phagocyte to "relish" the marked cell). Opson in ancient Greece referred to the delicious side-dish of any meal, versus the sitos, or the staple of the meal.