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from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. An antibody or product of complement activation in blood serum that causes bacteria or other foreign cells to become more susceptible to the action of phagocytes.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Any antibody that causes an invading species to be more susceptible to phagocytosis

from The Century Dictionary and Cyclopedia

  • n. A hypothetical substance, present in blood-serum, upon which the phagocytic action of the leucocytes is dependent.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. an antibody in blood serum that attaches to invading microorganisms and other antigens to make them more susceptible to the action of phagocytes


Latin opsōnāre, to buy provisions (from Greek opsōnein, from opson, condiment, delicacy) + -in.
(American Heritage® Dictionary of the English Language, Fourth Edition)



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