Studies On The Immunological Characteristics Of T Lymphocytes In Cord Blood

Objectives:Hematopoietic stem cells transplantation(HSCT) has made great progress in the treatment of malignant hematologic diseases,malignant tumors and genetic disorders et al since1960s. There are three main sources of stem cells: the bone marrow, the peripheral blood and the cord blood. The characteristics of cord blood make it an notable choice among transplantations of stem cells. Our studies focuse on the immunological characteristics of T lymphocytes in cord blood to explore the mechanisms of low incidence of graft-versus host disease(GVHD) and host-versus graft reaction(HVGR).Methods:1.By using methylcellulose culture method, the proliferative response of lymphocyte in cord blood are compared with that in adult peripheral blood.2. After stimulated with PHA and cultured in vitro for 72 hours, the levels of IFN-γ and IL-4 in the supernatants of cord blood lymphocytes and peripheral blood lymphocytes are detected by ELISA respectively.3. Lymphocytes from male cord blood and female adult peripheral blood are mixed to be cultured as the experiment group, and lymphocytes from male adult peripheral blood and female adult peripheral blood are mixed to be cultured as the control group. After cultured for 72 hours,the chromosomes are made from the cells with routine methods. Q banding technique is used to identify the Y chromosome. The percentage of mitotic figures with Y chromosome is observed.Result:1.The productions of CFU-TL in cord blood and peripheral blood are 297.6±47.3/2.5×105 and 385.3±31.2/2.5×105 respectively. The results show that the forming ability of CFU-TL in cord blood is lower than that in peripheral blood. It is suggested that the proliferative level of T lymphocyte in cord blood is lower than that in peripheral blood, and the cord blood has certain immune tolerance to the mismatched HLA antigen. It may be one of the causes of low incidence of GVHD in cord blood transplantation.2. The levels of IFN-γ and IL-4 of cord blood are significantly lower than those of peripheral blood, and the ratio of IFN-γ/ IL-4 of cord blood is lower than that of peripheral blood. The results show that the cellular immunity function of cord blood is lower than that of peripheral blood, and the Th2 function prevails over the Th1 function in cord blood. It suggests that the low ability to secrete cytokines(IFN-γ, IL-4) and the relatively prevailing state of Th2 function might be responsible for the decreased incidence of GVHD in cord blood transplantation.3. It is found that the percentage of mitotic figures with Y chromosome in the experiment group is higher than that in the control group. The result shows that cord blood lymphocytes can inhibit the mitosis of adult peripheral blood lymphocytes. It suggests that the inhibition may be responsible for the decreased incidence of HVGR in cord blood transplantation.Conclusions:1. That the forming ability of CFU-TL in cord blood is low may be one of the causes of low incidence of GVHD in cord blood transplantation.2. the low ability to secrete cytokines(IFN-γ, IL-4) and the relative prevailing state of Th2 function might be responsible for the decreased incidence of GVHD in cord blood transplantation.3. It may be one of the mechanisms of the low incidence of HVGR in cord blood transplantation that Cord blood lymphocytes has certain inhibition to adult peripheral blood lymphocytes.In short, the cord blood is a rich source of hematopoietic stem cells and can be used in clinical settings for hematopietic cell transplantation. In comparison with bone marrow and peripheral blood, cord blood displays decreased immune responses to alloantigens. With more studies on cord blood, we can be sure that cord blood will have an extensive application.