STUDIES OF RADIOIMMUNOASSAY FOR MEASUREMENT OF INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) BY USING ANTI-IGF-I MONOCLONAL-ANTIBODY

Radioimmunoassay system for measurement of insulin-like growth factor- I (IGF-I) was established by using anti-recombinant human IGF-I monocl onal antibody (MAb). This MAb is capable of recognizing not only human but also rat IGF-I. It was thus suggested that this RIA system can qu antify IGF-I in human and rat sera. MAb used in this paper was clarifi ed to be an antibody against the common epitope of C-region of human a nd rat IGF-I. Gly(32)-Ser(33)-Ser(34) sequence of C-region of IGF-I is discussed to be an antigenic determinant to which this antibody might specifically bind. MAb does not cross-react with proinsulin and insul in as well as anti-IGF-I polyclonal anbibody (PAb). And it is general that PAb has almost 2% cross-reactivity with IGF-II. But this MAb did not cross-react with IGF-II. Actually, the value of IGF-I measured by this system was lower than that measured by RIA using PAb.