That normally present in the blood, i.e., without stimulation by a known, specific antigen such as certain complement components; it is relatively thermolabile and reacts with various organisms.
Synonym: common opsonin, thermolabile opsonin.
Specific opsonin, antibodies formed in response to stimulation by a specific antigen, either as a result of an attack of a disease, or injections with a suitably prepared suspension of the specific microorganism.
Synonym: immune opsonin, thermostable opsonin.
(05 Mar 2000)