An isotype control antibody is a type of negative control used in experiments, particularly in flow cytometry, ELISA, and immunohistochemistry, to help distinguish specific antibody binding from non-specific binding. Isotype control antibodies have the same immunoglobulin class (IgG, IgA, IgM, etc.), subtype, and Fc region as the test antibody but lack the specificity for the target antigen. This allows researchers to account for non-specific interactions due to the Fc region or other aspects of the antibody structure.