Definition of precipitin in US English:



  • An antibody that produces a visible precipitate when it reacts with its antigen.

    • ‘Many reports and reviews have challenged the diagnostic value of serum precipitins for case finding.’
    • ‘Their specificity could be related to particular defined groups on the antigen and evaluated quantitatively with precipitin reactions and hapten inhibition of precipitation.’
    • ‘His laboratory was the first to emphasize the importance of precipitins to various peptide and polysaccharide antigens of Aspergillus fimigatus.’
    • ‘Serum agglutinins, precipitins, and complement-fixing antibodies can also be used to establish a diagnosis.’
    • ‘A negative serologic assay for precipitins does not rule out disease, as many factors can decrease the sensitivity of the test.’


Early 20th century: from the verb precipitate + -in.