Complement fixation

A process that helps to make antigen antibody complexes easier for phagocytes to digest.


Immunologic response in which an antigen combines with an antibody and its complement, causing the complement to become inactive. This phenomenon is the basis of certain blood tests to determine the presence of antibodies against specific diseases.


Blood test in which a sample of serum is exposed to a particular antigen and complement to determine whether antibodies to that particular antigen are present; used as a diagnostic aid (e.g., Wasserman test for syphilis).


The binding of complement by an antigen-antibody complex. This reaction is the basis of diagnostic tests for virus infection, fungus caused lung infection, and a number of other infectious diseases.


The binding of complement to the complex that is formed when an antibody reacts with a specific antigen. Because complement is taken up from the serum only when such a reaction has occurred, testing for the presence of complement after mixing a suspension of a known organism with a patient’s serum can give confirmation of infection with a suspected organism. The ‘Wasserman reaction for diagnosis of syphilis is a complement fixation test.


A common blood assay used to determine if antigen-antibody reactions have occurred. Complement that combines with the antigen-antibody complex becomes inactive and is unable to lyse (kill) red blood cells in vitro. The degree of complement fixation is determined by the number of red blood cells destroyed, which indicates the amount of free complement not bound to the antigen-antibody complexes. Complement fixation can measure the severity of an infection because it helps indicate the extent and effectiveness of antigen-antibody reactions occurring in the body.


 


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