文本框: IL-6 MEDIATES THE INHIBITORY EFFECT OF IGF-1 ON PHA-INDUCED APOPTOSIS IN CORD BLOOD T CELLS Law HKW and Lau YL Dept. of Paediatrics, The University of Hong Kong, Hong Kong, China Objective: Insulin-like growth factor-1 (IGF-1) inhibits PHA-induced T cells apoptosis in cord blood (CB) mononuclear cell (MC) through the reduction in Fas expression. We have reported that IL-6 can inhibit PHA-induced T cells apoptosis in purified CB CD3+ T cells. In this project, we further studied the role of IL-6 on PHA-induced apoptosis in CBMC and its role on the PHA-induced Fas expression in CD3+ T cells. Methods: CBMC were cultured in a serum free, insulin free medium (DMEM-F12) containing IGF-I + PHA ± anti-IL-6 antibodies. Apoptosis was determined by Annexin V and PI labelling and the T cell subsets were analysed by 3-colour flow cytometry. CD3+ T cells isolated by immunomagnetic separation were cultured in DMEM-F12 containing IGF-I, PHA and IL-6 in combinations and the Fas expression on T cell subsets were also analysed by flow cytometry. Results: In CBMC, anti-IL-6 antibodies significantly neutralised the effect of IGF-1 on PHA-induced apoptosis in each T cell subsets. In the purified T cells culture, the addition of IL-6 resulted in slightly higher percentage of cells expressing Fas but the difference did not reach statistical significance. Conclusion: These results support our hypothesis that IL-6 plays an important role in mediating the anti-apoptotic effect of IGF-1. However, IL-6 did not reduce PHA-induced Fas expression and further investigation is needed for other mechanisms involved. 1914