Radioimmunoassay of the serum thymus factor (STF)

The serum thymus factor (STF) is a polypeptide involved in the differentiation of T lymphocytes, the primary structure of which has been determined. Preliminary studies based on a semi-quantitative biological assay showed that the serum level of STF is modified in certain immune pathological situations. The authors have developed a radioimmunoassay of this factor. The STF was made immunogenic by combination with bovine albumin; the STF was labelled with iodine-125 previously alkylated with the Bolton Hunter reagent. The dosage sensitivity is such as to permit the detection of 2 pg of STF. However, the presence in the serum of molecules which interfere with the assay make it necessary to develop a method of extraction for the serum assay of STF. (author)