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At the component level, this diagram illustrates two different direct hemagglutination reactions, a positive viral hemagglutination assay (HA) reaction (above), and a negative viral HA reaction. The former involves a hemagglutinating virus, while the latter involves the implementation of a non-hemagglutinating virus, and how each interacts directly with red blood cells. Using this direct agglutination test, the agglutinating antibodies on the surface of the viral particles, react directly with antigens on the surface of the erythrocytes (RBCs), forming a lacey pattern, or visible clumps of particles, that can be seen accumulating in the bottom of the test tube, or well, as seen in the top reaction. A negative reaction, as seen on the bottom, reveals that there are no surface antigens present on the RBCs, which would bond to the virions, thereby, inducing an agglutination reaction, hence no hemagglutination occurs.
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CDC/ Dr. Frances Forrester
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Analytical, Diagnostic and Therapeutic Techniques and Equipment
Laboratory Techniques and Procedures
Hemagglutination Inhibition Tests
Biological Phenomena, Cell Phenomena, and Immunity
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