The evaluation of hydrocortisone antibodies produced in rabbits and sheep. I. Radioimmunoassay.

In response to an albumin-hydrocortisone hemisuccinate conjugate, antisteroid hormone antibodies have been produced in rabbits and sheep. Evaluation via competitive protein binding (radioimmunoassay) yielded the specificities of the antibodies to steroids. Steroids most closely related to the hapten bound to the antibodies, namely: hydrocortisone, cortisone, prednisolone, hydrocortisone sodiumsuccinate, THE and THF; in contrast, progesterone, 17 β-oestradiol, testosterone, cholesterol, and aldosterone failed to bind. Antigenicity and binding related to the C-17 α-hydroxyl and also the side groups on the D, C, B and A rings of the steroids. Least important were the changes in molecular structure or side groups of the A-ring. Finally, radioimmunoassay proved a sensitive method of evaluating antihormone antibodies.