precipitin reaction

precipitin reaction
precipitin reaction n the specific reaction of a precipitin with its antigen to give an insoluble precipitate

* * *

the formation of an insoluble precipitate by reaction of antigen and antibody; it occurs only with multivalent antigens and is dependent on electrolyte concentration, pH, temperature, and the relative concentrations of antigen and antibody, the amount of precipitate formed increasing to a maximum and then decreasing as the relative antigen concentration is increased.

Schematic of precipitin reactions with different proportions of antigen and antibody. Antigenic proteins that elicit antibody responses are depicted as having three different antibody-binding sites on their surface. Polyclonal antibodies with three different specificities (box, triangle, circle) are also depicted. (A), Under conditions of antigen–antibody equivalence, there is maximum cross-linking and visible precipitin formation. (B), With antigen excess, the resulting small soluble immune complexes do not form a visible precipitate. (C), With antibody excess, small soluble complexes are also formed; lattice formation is insufficient to cause visible precipitation. (D), Under conditions of equivalence but in the presence of monoclonal, rather than polyclonal, antibodies, each antigen binds only at a single site; there is no cross-linking and no visible precipitate.


Medical dictionary. 2011.

Look at other dictionaries:

  • precipitin reaction — noun : the specific reaction of a precipitin with its antigen to give an insoluble precipitate …   Useful english dictionary

  • precipitin test — n a serological test using a precipitin reaction to detect the presence of a specific antigen specif a test used in criminology for determining the human or other source of a blood stain * * * any serologic test based on a precipitin reaction… …   Medical dictionary

  • Precipitin — A precipitin is an antibody which can precipitate out of a solution. The Precipitin Reaction The precipitin reaction provided the first quantitative assay for antibody but is now made redundant by current technology and diagnostic techniques such …   Wikipedia

  • precipitin test — noun : a serologic test using a precipitin reaction to detect the presence of a specific antigen; specifically : a criminological test determining the human or other source of a blood stain show by a precipitin test that this is dog blood Erle… …   Useful english dictionary

  • precipitin — An antibody that under suitable conditions combines with and causes its specific and soluble antigen to precipitate from solution. SYN: precipitating antibody. * * * pre·cip·i·tin pri sip ət ən n any of various antibodies which form insoluble… …   Medical dictionary

  • precipitin — n. any antibody that combines with its antigen to form a complex that comes out of solution and is seen as a precipitate. The antibody antigen reaction is specific; the precipitin reaction is therefore a useful means of confirming the identity of …   The new mediacal dictionary

  • reaction — 1. The response of a muscle or other living tissue or organism to a stimulus. 2. The color change effected in litmus and certain other organic pigments by contact with substances such as acids or alkalies; also the property that such substances… …   Medical dictionary

  • reaction of identity — a reaction pattern seen in double diffusion in two dimensions: the precipitin lines between the antigen wells and the antiserum well stop at their point of intersection, indicating that the antigen samples are identical. See also r. of… …   Medical dictionary

  • reaction of nonidentity — a reaction pattern seen in double diffusion in two dimensions: the precipitin lines between the antigen wells and the antiserum well cross, indicating that the antigen samples have no antigenic determinants in common. See also r. of identity and… …   Medical dictionary

  • reaction of partial identity — a reaction pattern seen in double diffusion in two dimensions: one of the precipitin lines between the antigen wells and the antiserum well stops at the point of intersection, whereas the other continues past it, indicating that the antigen… …   Medical dictionary

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”