Phenotypic Analysis of Lymphocyte Subpopulation in Cord Blood

Woo, Chan Wook; Lee, Kwang Chul; Cho, Yoon Jeong; Kim, Young Tae

Abstract

BACKGROUND: Cord blood transplantation has generated much enthusiasm because of the low incidence of GVHD(graft-versus-host disease), even in HLA(Human Leukocyte Antigen) mismatched situations, owing to intrinsic defects in mature T cell functions, and human cord blood is a constantly and easily obtainable source for hematopoietic stem cell. This study was undertaken to elucidate the possible mechanisms of low GVHD incidence observed when cord blood is used for stem cell transplantation. Based on current knowledge of the phenotypic correlates with functional subtypes of peripheral blood lymphocytes, we evaluated lymphocyte subpopulation in cord blood.
METHODS
The 25 cord blood and 20 peripheral blood of adult control were included in this study. Monoclonal antibodies(MAb) conjugated with fluorescein-isothiocynate(FITC), phycoerythrin(PE) were used in this study. Heparinized whole blood was stained with mAbs using the whole blood lysis method. We used FACScan flow cytometer with argon laser tuned at 488 nm. Analysis was done by either Simulset or lysis II research software. RESULT: 1) The means of WBC and lymphocyte content were higher in cord blood than in adult blood(p<0.05). 2) The overall percentages of cord blood T(CD3+) cells, B(CD19+) cells, NK(natural killer)(CD16+/CD56+) cells were not different from adult controls. 3) The CD4+ : CD8+ ratio of cord blood was higher than thar of adult controls(2.7 in cord bloods versus 1.8 in adults). 4) The majority of the cord blood cells, both CD4+ and CD8+, co-expressed the CD45RA+ (naive) molecule. 5) The CD57, an antigen present on a subpopulation of NK cells, is absent in cord blood.
CONCLUSION
We determined that cord blood contained mainly naive T lymphocytes to be predominantly suppressor cells. We found reduced alloproliferative, allostimulatory and allocytotoxic capacity of cord blood lymphocytes. Therefore, the GVHD may be less readily induced in cord blood transplantation, even in the face of HLA difference.