AN IMMUNORADIOMETRIC ASSAY FOR THYMOSIN ALPHA-1

An Immunoradiometric assay for thymosin alpha 1(1-28) was developed us ing a monoclonal and a polyclonal antiserum which were raised against synthetic thymosin a 1(1-28) and thymosin alpha 1(16-28), respectively . A monoclonal antibody, specific for the (acetylated serl) 1-5 sequen ce of thymosin alpha 1, was immobilized on polystyrene beads for the s olid phase, and a polyclonal antiserum specific for the 16-28 sequence was employed. This method relies on the formation of an immune comple x consisting of a I-125-labelled anti-rabbit IgG goat antibody, polycl onal antiserum, thymosin (a)lpha 1, and the solid phase monoclonal ant ibody. Radioactivity on the solid phase is directly proportional to th e amount of thymosin a 1 present in the specimen. The minimal detectio n limit of this assay system was approximately 1.9 pg/ml. The mean val ues of thymosin alpha 1 in plasma of healthy subject, ranging in age f rom 0 to 3 years was approximately five fold higher than that of highe r ages. HPLC analysis of plasma of a healthy subjects revealed a singl e immunoreactive form which eluted with the same retention time as tha t of synthetic thymosin alpha 1. This assay will be extremely useful f or the measurement of thymosin alpha 1 in biologic fluids acid tissues .