Ask AI: Why is mouse IgG1 needed in flow cytometer experiment when identifying the number of cells in the R2 population that express IL-4?

Mouse IgG1 serves as an isotype control in flow cytometry experiments to determine the level of background or non-specific binding of the primary antibody used in the experiment. In this case, the primary antibody being used to identify IL-4 expressing cells is likely also a mouse IgG1 antibody. By including a control sample that is stained with an isotype control antibody of the same isotype as the primary antibody, researchers can determine the level of non-specific binding due to the primary antibody itself. This allows for more accurate identification of the R2 population that expresses IL-4, as any non-specific binding due to the primary antibody can be subtracted from the total number of cells in the R2 population. Overall, including a mouse IgG1 isotype control in flow cytometry experiments is an important quality control step to ensure specificity of the results.