Preparation of monoiodinated interleukin-1 beta and its use in a radioimmunoassay.

Polyclonal anti-interleukin-1 beta (IL-1 beta) sera raised in sheep and in rabbits bound to unlabelled IL-1 beta. IL-1 beta radioiodinated using chloramine-T or Bolton-Hunter procedures was bound by the anti-IL-1 beta sera but was not displaced by unlabelled IL-1 beta suggesting that IL-1 beta was damaged during iodination procedures, resulting in alterations to the immunological properties of the tracer. Iodination using the mild oxidant N-bromosuccinimide, followed by extensive tracer purification to remove the unlabelled IL-1 beta, produced a tracer with a specific activity of 89 microCi/micrograms (0.83 atoms iodine/molecule IL-1) which was fully displaced by unlabelled IL-1 beta, allowing the development of a sensitive and specific radioimmunoassay for IL-1 beta. The radioimmunoassay has been used to quantify intracellular IL-1 beta and IL-1 beta release by peripheral blood monocytes stimulated with endotoxin.