Antibodies, also known as immunoglobulins (Ig), are large Y-shaped proteins produced and used by the immune system to identify specific biomolecules, called antigens. The recognition between an antibody and an antigen is usually described as a lock-key mechanism: the paratope (analogous to a lock) on each tip of the “Y” of an antibody precisely binds to one particular epitope (analogous to a key). The degree to which an antibody’s binding site will interact with an antigen is called its affinity.
In bioassays, antibodies are traditionally divided into two classes, primary and secondary, based on whether they directly bind to antigens or not. Primary antibodies directly bind to the biomolecule of interest. They can be monoclonal, targeting a specific antigen, or polyclonal, targeting several antigens. Secondary antibodies, on the other hand, bind to another (primary) antibody, which is bound to a target, or an antigen.
Primary antibodies can be very useful for the detection of biomarkers for diseases such as cancer, diabetes, Parkinson’s and Alzheimer’s disease. With the aid of secondary antibodies, which are usually conjugated to a fluorophore or reporter enzyme, primary antibodies can be used for quantification of a target. Wide applications of primary and secondary antibodies have been found in Western blotting, flow cytometry and ELISA.
Antibodies have become a versatile and invaluable research tool in various scientific fields from cancer research to neuroscience and cell signaling pathways. Here at AAT Bioquest, affinity and purity are the focal points of our antibody development, producing antibody reagents in various formats that are of optimal quality, target specificity and flexibility