Role of insulin-like growth factor-1 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 proliferating cells. This was documented by kinetics data obtained from the first proliferation round of PHA-stimulated lymphocytes, in which addition of IGF-1 reduced G1-phase length, without changing G0-phase, S-phase or cloned size. The data were confirmed in 10-day culture of stimulated lymphocytes where IGF-1 only accelerated cell proliferation without modifying the area enclosed by the proliferation curve. As IGF-1 is under the control of growth hormone, our results suggest that some of the immuno-regulation effects ascribed to growth hormone in vivo could be produced by IGF-1.