In a flow cytometric crossmatch, what is the purpose of the forward scatter versus side scatter plot?

In flow cytometry, the forward scatter (FSC) versus side scatter (SSC) plot serves a critical role in analyzing different cell populations based on their physical characteristics. The forward scatter detects the size of the cells, while the side scatter provides information about the granularity or internal complexity of the cells.

The correct purpose of the forward scatter versus side scatter plot is that it allows the identification and gating of live lymphocytes specifically, aiding in the exclusion of other blood cells that do not fit the profile of lymphocytes. This process is essential for ensuring that subsequent analyses focus on the relevant cell population for the study in question, such as assessing the immune response in a crossmatch scenario.

In terms of potential ambiguities with the other options, while determining size and scatter characteristics is a valuable aspect of flow cytometry, the more precise function in this context focuses on isolating live lymphocytes. T cell and B cell distinction can be achieved through additional markers and fluorescence characteristics rather than through the FSC versus SSC plot alone. Lastly, quantifying the level of anti-donor IgG antibody typically requires a different approach involving specific assays or staining strategies, rather than relying on the general size and granularity data from the FSC versus SSC plot.