1. antigen-antibody interactions cause a conformational shift in immunoglobulin structure promoting binding of C1 and subsequent activation of the complement cascade, complement fixation.
2. an immunoassay using reference antibodies with complement fixation and lysis of red blood cells as an indicator of detectable antigen. The degree of hemolysis affects the optic density of the sample, which can be measured and compared with a standard reference concentration curve.
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