Human umbilical cord blood, which in the past was discarded with the placental tissue,provides a convenient source of fetal hemopoietic cells for scientific analysis and clinical use.Cord blood cells are immature compared to analogous populations in adult peripheralblood. Cord blood B lymphocytes display unique phenotypic and functional characteristics.The antigens CD1C, CD38, CD5, and CD23, although normally expressed on only a smallpercentage of circulating B cells in adults, are highly expressed on cord blood B cells. Recentstudies have demonstrated that whereas cord blood B cells are functionally naive, theirpotential is similar to that of adult B cells if optimal T-cell help is available. Thus, the failureof B-cell responses in cord blood is due to the T cells. The functional abnormalities of T cellsfrom newborns can be summarized as a dominance of the effects of TH0 cells. Thus, thecytokines produced are immunosuppressive rather than mediating helper activity for B cells.NK activity in cord blood is also depressed compared to that in adults. Cord blood is a veryrich source of hemopoietic progenitor cells. The spectrum of progenitors shows a predominanceof early progenitor cells when compared with bone marrow. These cells provide analternative source to adult bone marrow for stem cells to use for hemopoietic reconstitutionand as targets in the treatment of hereditary deficiencies by gene therapy. These featuresmake cord blood a unique research tool to investigate hemopoietic ontogeny and a uniqueclinical tool for transplantation.
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