The indirect method, aside from its greater sensitivity, also has the advantage that only a relatively small number of standard conjugated (labeled) secondary antibodies needs to be generated. For example, a labeled secondary antibody raised against rabbit IgG, which can be purchased "off the shelf", is useful with any primary antibody raised in rabbit. This is possible because all rabbit IgG in this example would have the same Fc (constant) region, thus even with a small number of anti-rabbit secondary antibodies generated, each could adhere to any primary rabbit antibody. This is particularly useful when a researcher is labeling more than one primary antibody, whether due to polyclonal selection producing an array of primary antibodies for a singular antigen or when there is interest in multiple antigens. With the direct method, it would be necessary to label each primary antibody for every antigen of interest.