The establishment of a radioimmunoassay

Abstract

Yalow and Berson were the first to develop a RIA¹³⁹. Naturally it happened to be for insulin, since the same researchers in 1956 had proven that conventional insulin therapy induced circulating insulin-binding antibodies in all patients treated, as demonstrated by the ability of their serum (and immunoglobulin fractions) to bind ¹³¹I-labelled insulin⁷. A detailed report¹³⁹ outlined the essential requirements needed to establish this RIA: raising antibodies with sufficiently high affinity to permit a low detection limit of the assay and sufficiently high capacity for practical routine work, preparing a labelled substance with high reactivity towards the antibodies and, last but not least, to have available standards of the substance to be measured. For the first time guinea pigs were used to raise insulin antibodies and they have remained the animal of choice for the preparation of insulin antibodies in spite of their drawbacks — small blood volumes only obtainable by heart puncture or eye blood sampling. The outstandingly positive characteristics of their antibodies are the combined high affinity and capacity, allowing low detection limit, high sensitivity and high dilution of the antiserum. The latter characteristics may be a consequence of the great differences between the bovine, porcine and human insulin compared to guinea pig insulin (approx. 19 amino acids out of 51), rendering the exogenous insulins highly immunogenic in the guinea pig.