Since the discovery by César Milstein and George Köhler in 1975 on the construction of a continuously growing cell line expressing a specific, predefined monoclonal antibody, it has been possible to produce unlimited amounts of pure and specific monoclonal antibodies.
By using monoclonal antibodies in assay development, specific to a single epitope on a single molecule, the sensitivity and specificity could now be tailored by careful epitope selection. This has caused a major increase in diagnostic assay performance and quality. For example, when proinsulin was detected in 1959 as the biosynthetic precursor for insulin, it quickly became clear that assays using polyclonal antibodies would detect both insulin and proinsulin to varying degrees. A number of studies since then have shown that it is not possible to assess insulin status in conditions such as type 2 diabetes and impaired glucose tolerance with these non-specific insulin assays. Today ́s insulin assays, based on monoclonal antibodies, can be developed without cross-reaction to proinsulin, to yield very sensitive and specific diagnostic tools enabling valuable insulin status assessment.