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Agglutination, specifically, hemagglutination, is the clumping together of red blood cells. Insoluble particles (RBC) combine with soluble compounds (antibodies) to form macroscopically/microscopically visible clumps (agglutinins).
When studying agglutination, there are a few terms that should be reviewed and understood:
  • Prozone - excess antibody to the available amount of antigen (no agglutination is a result)
  • Zone of Equivalence - optimal amounts of both antibody and antigen (results in agglutination)
  • Postzone - excess antigen to the available antibody (no agglutination is a result)

The curve in the graph to the right depicts the formation of immune complexes as antibody concentration (y-axis) and antigen availability (x-axis) work in conjunction to form visible agglutination.