PeproTech’s polyclonal antibodies are purified through the isolation of specific polyclonal antibodies from antiserum by antigen affinity chromatography. This procedure exploits the specificity of the antibody-antigen interactions and typically yields >95% pure specific antibodies. Normally, the sera from host animals after immunization with cytokines contain only small amounts of cytokine-specific antibody (<5%), which cannot be effectively isolated by standard purification procedures (e.g. ion exchange chromatography) or by non-antigen-specific affinity procedures, such as Protein A/G affinity purification. The large quantities of unrelated IgGs found in these inferior preparations can considerably increase the background when the antibody is used in analytical procedures such as ELISA, neutralization, immunohistochemistry, and Western blotting. Therefore, the use of the superior antigen affinity-purified antibody preparations can help alleviate background in these analytical procedures.