Antibodies bind with high specificity to antigens used to challenge the immune system, but they may also show cross-reactivity by binding to other antigens that share chemical properties with the original antigen Injection of an antigen into an animal will result in a polyclonal antibody response in which different antibodies are produced that react with the various epitopes on the antigen

Polyclonal antisera are useful for some types of laboratory assays, but other assays require more specificity. Diagnostic tests that use polyclonal antisera are typically only used for screening because of the possibility of false-positive and false-negative results

Be able to compare the method of development, use, and characteristics of monoclonal and polyclonal antibodies; explain the nature of antibody cross-reactivity and why this is less of a problem with monoclonal antibodies; describe various types of assays used to find antigen-antibody complexes.