Polyclonal antibodies are considered heterogeneous, because they are obtained from different immune cell (B-cell) resources. They are a combination of immunoglobulin molecules secreted against a specific antigen, each identifying a different epitope on that antigen.
Polyclonal antibodies are produced by injecting an antigen into a mammal. This induces the B-cells to produce immunoglobulins specific for the antigen. Immunoglobulin G (IgG) is composed of two identical heavy chains. This polyclonal IgG is purified from the mammal’s serum. Polyclonals are typically produced by immunization of a rabbit, but larger mammals, such as goats, are used to obtain larger amounts of serum.
Polyclonal antibodies are sensitive because they bind to more than one epitope of the SAME antigen. This means that they are NOT as selective as monoclonal antibodies and this may produce non-specific, or background, staining.