Abstract

Low ambient temperaturewith the onset ofwinter can disturb radio immuno assay due to increased association constant of antibody

Author(s): Aminu Deen

In our laboratory, Radio-immuno assay(RIA) for quantification of estradiol-17â was standardized using antioestradiol( Prof.Niswender, Colorado StateUniversity,USA) and 2,4,6,7,16,17-3Hoestradiol(AmershamBiosciences Ltd., U.K.) as tracer. Antibody titer was determined to give maximumbinding of 50%with the tracer. This titer was used for assays between July to November 2004, all of which exhibited a perfect displacement of tracer by increasing concentration of calibrators. With the onset of winter, assay procedure was suddenly deteriorated, resulting into no displacement of tracer by calibrators. Buffers, standards and other chemicals were prepared freshly but yielded no improvement in repeat trials, the observations of the results obtained in repeated trials revealed that there were significant displacement of tracer in only 2-3 of highest concentration calibrators out of total 10 calibrators. For remaining 7 calibrators, displacement was not visible, though the binding of tracer was very high.While facing this problem, we come across to an important aspect of antibody-heptanes interaction, that low temperature increases association constant of antibody. Working on this point, the antibody titer was recalibrated for winter atmospheric conditions. Itwas found to increase by 10 folds. Successful re-standardizationwas accomplished with altered antibody titer. It was concluded that low ambient temperature might disturb your RIA due to increased association constant(Ka) of antibody.