Abstract: Abstract: Objective To study the biological characteristics of mesenchymal stem cells(MSCs) derived from human cord(UCMSCs) and inhibitory effect on the transformation of lymphocytes from allogeneic Umbilical Cord Blood . Methods UCMSCs were isolated from umbilical cord ,the purity of MSC was analyzed by ICC.The effect of UCMSCs on the transformation of lymphocytes from allogeneic UCB was tested by the method of MTT. Results The morphological feature of the third passage’s UCMSCs(P3-UCMSCs) displayed an uniform fibroblast-like phenotype. The doubling time of P3-MSCs was 51.6 hours,they expressed MSCs-related antigen CD29 but did not express hematopoietic cell antigen CD34.The histochemical staining of P3-UCMSCs showed that PAS and NBE were positive but POX was negative. It indicated that the fibroblast-like cells induced and expanded from human cord in our experiment were MSCs ;UCB-lymphocyte transformation was suppressed when UCMSCs were cultured together with UCB-lymphocytes and the suppression effect was related with UCMSCs numbers plated in eath well, the suppression rate reached 60.8% when 2000 UCMSCs were plated. Conclusion UCMSCs had an immunomodulatory function. UCMSCs could suppress the transformation of lymphocytes from allogeneic UC and the suppression function seemed dependent on MSC numbers plated in each well.

Key words: Key Words: Umbilical cord, Mesenchymalstem cell, Immunomodulatory suppression