Polyclonal Antibodies from Affinity Biologicals Inc.
For reasons of price and performance, polyclonal antibodies are often the reagents of choice in laboratory applications. Affinity Biologicals Inc. (ABI) offers an extensive line of antibodies to haemostasis related proteins. Although ABI does offer some murine monoclonal antibodies, most antibodies are polyclonal antibodies raised in sheep and goats. Because polyclonal antibodies contain antibodies to multiple recognition sites (epitopes) on an antigen the apparent affinity and avidity of antigen-antibody interactions is very high. This results in greater sensitivity and also means that the antigen is more likely to be recognized after denaturation or proteolytic processing. These are important considerations for applications such as immunoblotting from denaturing gels such as SDS-PAGE and in immunohistochemistry of fixed cells and tissues. Polyclonal antibodies are excellent for use in immunoassays where high sensitivity is required and are frequently the preferred reagent for immunoprecipitation techniques and activity neutralization assays. At ABI we have had good success using our polyclonal antibodies immobilized to resins to specifically immuno-deplete target proteins from citrated plasma and to recover the target protein from these resins with excellent recovery of activity.
Most ABI antibodies are available in several different formats, each differing in the level of refinement.
Whole IgG is the base level product and refers to IgG antibodies purified from antiserum (usually sheep or goat) using multiple precipitation and dialysis steps. The purity of the IgG is typically 90% and is provided in a solution of HEPES buffered saline containing 50% glycerol (v/v). The titre is essentially the same as the starting antiserum and each vial typically contains the amount of IgG recovered from one millilitre of antiserum. This level of product is generally intended for use in applications such as immunoprecipitation, immunoelectrophoresis, immuno-depletion and activity neutralization assays.
Affinity-purified IgG are antibodies further purified using immobilized antigen. Affinity-purification is an enrichment process in which whole IgG is passed over a resin to which antigen has been covalently attached. Non-reactive antibodies are washed away and specific antibodies are eluted under conditions that disrupt the antigen-antibody interaction. The result is a very high-purity product with a substantially higher titre than whole IgG. This level of product is intended for applications such as immunoblotting, immunostaining of cells and several types of immunoassays where the higher signal-to-noise ratio achieved with this enriched product is required.
Enzyme labeled IgG is either whole IgG or affinity-purified IgG that has been conjugated with Horseradish Peroxidase as a reporter enzyme. These products are intended for use as labeled primary antibodies in applications such as immunoassay and immunoblotting.