Biotin-conjugated IgG fraction of polyclonal goat antiserum to Mouse IgG, IgA and IgM, heavy and light chains, adsorbed for human cross-reactivity. In immunocytochemical and immunohistochemical staining of monoclonal mouse monoclonal antibodies in the presence of human cell or serum components at the cellular and subcellular level. As a second step an avidin or streptavidin conjugate of the user's choice has to be used. This immunoconjugate is not pre-diluted. The optimum working dilution of each conjugate should be established by titration before being used. Excess labelled antibody must be avoided because it may cause high unspecific background staining and interfere with the specific signal. Working dilutions are usually between 1:100 and 1:500; in ELISA and comparable non-precipitating antibody-binding assays between 1:1,000 and 1:10,000.