(1) Secondary antibodies react with primary antibodies. Thus, secondary antibodies should be
                    against host species of primary antibodies. E.g. If the primary antibody is derived from rabbit, the relevant
                    secondary antibody should be against rabbit. E.g. goat anti rabbit or donkey anti rabbit.
                (2) Choose secondary antibody conjugates according to the experimental type, e.g. ELISA, WB, IHC
                    etc. Common enzyme conjugated secondary antibodies are labelled by HRP, AP etc. Fluorescin or dye labelled
                    secondary antibodies are applied in immunofluorescence and flow cytometry(e.g. FITC, Cy3).