Testing for cross reactivity involves: - Control Experiments: Using negative controls to ensure specificity. - Western Blot: To check if the antibody binds to proteins of the expected molecular weight. - Blocking Peptides: Using the specific peptide that the antibody was raised against to block its binding, thereby confirming specificity. - Pre-adsorption: Pre-incubating the antibody with potential cross-reactive antigens to see if binding is reduced.