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[op-suh-nin] /ˈɒp sə nɪn/
noun, Immunology.
a constituent of normal or immune blood serum that makes invading bacteria more susceptible to the destructive action of the phagocytes.
Origin of opsonin
1900-05; < Latin opsōn(ium) victuals (< Greek opsōnía, derivative of opsōneîn to buy provisions) + -in2
Related forms
opsonoid, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for opsonin
Historical Examples
  • In the case of diphtheria, the antitoxin appears to be more efficacious than an opsonin.

  • opsonin is what you butter the disease germs with to make your white blood corpuscles eat them.

    The Doctor's Dilemma George Bernard Shaw
  • The "opsonin," or "relish," is something exuded into or produced in the blood fluid when the attacking microbe arrives.

    More Science From an Easy Chair

    Sir E. Ray (Edwin Ray) Lankester
British Dictionary definitions for opsonin


a constituent of blood serum that renders invading bacteria more susceptible to ingestion by phagocytes in the serum
Derived Forms
opsonic (ɒpˈsɒnɪk) adjective
Word Origin
C20: from Greek opsōnion victuals
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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opsonin in Medicine

opsonin op·so·nin (ŏp'sə-nĭn)
An antibody in blood serum that causes bacteria or other foreign cells to become more susceptible to the action of phagocytes.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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