EVIDENCE FOR SUPPRESSION OF IMMUNE FUNCTION BY INSULIN-LIKE GROWTH-FACTOR-I IN DWARF RATS IN-VIVO

These studies were undertaken to investigate the effects of increasing or decreasing IGF-1 levels on aspects of immune function in rats. Fem ale dwarf rats were treated with recombinant human IGF-1 or with a pot ent sheep anti-IGF-serum. Body weight, thymus weight and spleen weight increased with IGF-1 treatment (p < 0.001), while there was no effect of anti-IGF-1 treatment when compared with the appropriate normal she ep serum (NSS) treated controls. IGF-1 treatment significantly decreas ed WBC and RBC counts, but increased the ratio of CD4(+):CD8(+) T-cell s. Anti-IGF-1 serum had no effect on these parameters compared with MS S. However anti-IGF-1 was associated with increased T-cell numbers, de creased natural killer cells, and enhancement of the animals' ability to produce specific IgG in response to injection of keyhole limpet hae mocyanin (KLH). These results indicate that IGF-1 may suppress immune function although increasing the size of immune organs such as spleen.