ROLE OF INSULIN-LIKE GROWTH-FACTOR-I ON THE KINETICS OF HUMAN-LYMPHOCYTES STIMULATION IN SERUM-FREE CULTURE-MEDIUM

In a serum-free medium addition of insulin-like growth factor-1 (IGF-1 ) consistently enhanced lymphocyte proliferation response to PHA in a dose-dependent fashion. This effect was produced by an acceleration in the expression of clone expansion and not in the number of proliferat ing cells. This was documented by kinetics data obtained from the firs t proliferation round of PHA-stimulated lymphocytes, in which addition of IGF-1 reduced G(1)-phase length, without changing G(o)-phase, S-ph ase or cloned size. The data were confirmed in 10-day culture of stimu lated lymphocytes where IGF-1 only accelerated cell proliferation with out modifying the area enclosed by the proliferation curve. As IGF-1 i s under the control of growth hormone, our results suggest that some o f the immunoregulation effects ascribed to growth hormone in vivo coul d be produced by IGF-1.