Use of radioisotopic immunoassay to evaluate locally produced secondary antibodies as a separation system for some in vitro investigations in nuclear medicine

Radioimmunoassay (RIA) is one of the in vitro diagnostic methods in nuclear medicine. The most important factor in RIA reagents to be considered is the antibody production, as specific antibodies with high affinity are the backbone of RIA techniques. In this experiment iodine (I125) radiolabelled antigens were used to evaluate locally produced donkey anti-sheep serum (DASS) as a separating agent in RIA. Two local donkeys were immunized with non-immunized sheep immunoglobulin (IgG) to produce donkey anti-sheep secondary antibodies. Samples were collected from the two donkeys, purified, dialysed, qualitatively tested for the presence of antibodies, which were then quantitatively evaluated and utilized as precipitating agent in RIA by adding the primary antibodies. Using RIA methodology the antibodies were titrated against three different analytes (thyroxine T4, triiodothyronine T3, and progesterone) for which the primary antibodies already raised in sheep in order to be used as secondary antibody separation system for them. The titre was found to be 1/40 for the T4 and progesterone while 1/6 for T3. Then local antibodies replaced the commercial ones using the suitable titre for each analyte. Upon comparison of the obtained results of patient samples and quality control (Bio rad) using the local DASS and commercial ones. The correlation coefficient (r) for T4, T3 and progesterone were 0.950, 0.878 and 0.950 respectively. Six liters of antiserum were collected in a period of one year. Considering the workload of the country for the above mentioned three analytes this amount is enough to meet the needs for the the next ten years in Sudan. this production will save a lot of hard currency paid for importing DASS from abroad. (Author)