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Comparison of three hemolytic plaque assays using sheep and mouse erythrocytes as antigens in rats
Abstract:
Several hemolytic plaque assays using spleen cells from rats immunized with sheep or mouse erythrocytes were compared. Modifications of the assays were made to define optimal conditions. Mrbc in assays with guinea pig complement yield a much reduced number of plaques than is observed when human complement is used. In contrast, no difference in numbers is noted with Srbc regardless of complement source. The use of Srbc in an assay technique that does not employ agarose is more sensitive than techniques that require agarose; the result is a 50-100% increase in the number of plaques. This increase in plaque number was observed with either guinea pig or human complement. In contrast, there was considerable clumping of Mrbc in the absence of agarose which tended to obscure distinct plaque formation. Increased sensitivity of plaque development for Srbc in the absence of agarose was due to increased numbers of direct (IgM) plaque detection and not to concomitant detection of cells producing IgG (indirect plaques). Maximal detection of plaques with Mrbc was observed when human complement was used in assays containing agarose. These assays gave a threefold increase in plaque numbers when compared with assays without agarose. It is evident from the above that the most sensitive and reproducible hemolytic plaque assay to be used by an investigator will depend primarily upon the antigen, and on reagents selected for the test.
Insights
Optimizing hemolytic plaque assays is crucial for accurate results. The study found that assay sensitivity depends on the specific antigen and chosen reagents, impacting plaque detection for mouse and sheep red blood cells.
Area of Science:
- Immunology
- Cellular immunology
Background:
- Hemolytic plaque assays are vital for quantifying antibody-producing cells.
- Standardization of these assays is necessary for reliable results.
Purpose of the Study:
- To compare different hemolytic plaque assay conditions.
- To identify optimal parameters for sensitive and reproducible plaque detection.
Main Methods:
- Comparison of hemolytic plaque assays using rat spleen cells immunized with mouse red blood cells (Mrbc) and sheep red blood cells (Srbc).
- Evaluation of different complement sources (guinea pig vs. human) and the use of agarose in the assay.
- Assessment of direct (IgM) and indirect (IgG) plaque formation.
Main Results:
- Mouse red blood cells (Mrbc) showed reduced plaque numbers with guinea pig complement compared to human complement.
- Sheep red blood cells (Srbc) assays were not affected by complement source.
- A 50-100% increase in Srbc plaque numbers was observed without agarose, primarily due to enhanced direct IgM plaque detection.
- Mrbc assays with agarose and human complement yielded maximal plaque detection, a threefold increase compared to assays without agarose.
- Clumping of Mrbc in the absence of agarose obscured plaque formation.
Conclusions:
- The choice of antigen (Mrbc vs. Srbc) and reagents significantly influences hemolytic plaque assay sensitivity and reproducibility.
- Assay conditions, including the presence of agarose and the type of complement, must be optimized based on the specific red blood cell antigen used.
- The study highlights the importance of tailored assay design for accurate enumeration of antibody-secreting cells.