[ 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 formsop·so·noid, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for opsonin

  • In the case of diphtheria, the antitoxin appears to be more efficacious than an opsonin.

  • 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


/ (ˈɒpsənɪn) /


a constituent of blood serum that renders invading bacteria more susceptible to ingestion by phagocytes in the serum

Derived Formsopsonic (ɒpˈsɒnɪk), adjective

Word Origin for opsonin

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

Medicine definitions for opsonin


[ ŏpsə-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.