16.3.3: Serologic Tests for Infectious Mononucleosis

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During infectious mononucleosis, caused by the Epstein-Barr virus (EBV), the body produces non-specific heterophile antibodies which are not found in normal serum. As it turns out, these heterophile antibodies will cross react with glycoprotein antigens found on the surface of red blood cells (RBCs) of various animals, including horses, sheep, and cows, causing the RBCs to agglutinate. These cross-reacting glycoprotein antigens are often called Paul-Bunnell antigens after their discoverers.

The infectious mononucleosis serologic test demonstrated today is a rapid qualitative test for infectious mononucleosis called the ASI Color Mono II TestÂ®. The mono reagent in this test is a suspension of dyed, color-enhanced, preserved horse erythrocytes. The Paul-Bunnel antigens in the cell membrane of these horse erythrocytes are highly specific for mononucleosis heterophile antibodies and act as the "known antigen." Agglutination of the erythrocytes after adding the patient's serum indicates a positive test (see Fig. \(\PageIndex{1}\)). Quantitative tests may be done to determine the titer of heterophile antibodies and follow the progress of the disease.

Photograph of a positive qualitative test for infectious mononucleosis showing clumping of the horse erythrocytes. — Figure \(\PageIndex{1}\): **Positive Qualitative Serologic Test for Infectious Mononucleosis**. Clumping of the horse erythrocytes containing Paul-Bunnel antigens in their cell membrane indicates the person's serum contains heterophile antibodies. ( Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0 )

Contributors and Attributions

Dr. Gary Kaiser (COMMUNITY COLLEGE OF BALTIMORE COUNTY, CATONSVILLE CAMPUS)