RESUMO
OBJECTIVE: To investigate the immune reconstitution by the transplantation of human umbilical cord blood CD34+ cells in the NOD/SCID mouse. METHODS: Mononuclear cells (MNC) were isolated from human fresh cord blood and CD34+ hematopoietic stem cells were selected by magnetic activated cell sorting method. The selected cells were transplanted via tail vein injection into 16 NOD/SCID mice after sublethal whole-body irradiation. Four mice were sacrificed respectively at 4th, 6th, 8th and 10th week after the transplantation, the harvested spleen and peripheral blood cells were used to cell phenotype analysis and humoral immune analysis, respectively. There were 14 mice in another two groups, 7 mice did not receive the transplantation after irradiation, 7 were used as blank control (no irradiation, no transplantation). RESULTS: The mice without transplantation all died within 2 weeks after irradiation. The survival rate of the mice with transplantation was 37.5% at 6th week after the irradiation, while the survival rate of blank control was 100%. At 4th, 6th, 8th and 10th week, the percentage of human CD45+ cells in transplantation group were 4.7 +/- 1.23, 9.22 +/- 2.07, 12.34 +/- 2.38, 8.14 +/- 2.36, respectively, and the percentage of CD19+ B lymphocytes were 1.07 +/- 0.50, 2.17 +/- 0.95, 3.34 +/- 0.90, 1.67 +/- 0.90, respectively. 10 weeks after the transplantation, human CD19+ B lymphocytes distribution were found in the transplanted mice spleen. CONCLUSION: The human-mouse chimeric immune model can be built in irradiated NOD/ SCID mice by the transplantation of human cord blood CD34+ cells. CD34+ cell differentiation declined with time, which might be due to the lack of appropriate cytokines.
