HEMATOPOIETIC AND LYMPHOID PROGENITOR CELLS IN HUMAN UMBILICAL-CORD BLOOD

Human umbilical cord blood, which in the past was discarded with the p lacental tissue, provides a convenient source of fetal hemopoietic cel ls for scientific analysis and clinical use. Cord blood cells are imma ture compared to analogous populations in adult peripheral blood. Cord blood B lymphocytes display unique phenotypic and functional characte ristics. The antigens CD1C, CD38, CD5, and CD23, although normally exp ressed on only a small percentage of circulating B cells in adults, ar e highly expressed on cord blood B cells. Recent studies have demonstr ated that whereas cord blood B cells are functionally naive, their pot ential is similar to that of adult B cells if optimal T-cell help is a vailable. Thus, the failure of B-cell responses in cord blood is due t o the T cells. The functional abnormalities of T cells from newborns c an be summarized as a dominance of the effects of THO cells. Thus, the cytokines produced are immunosuppressive rather than mediating helper activity for B cells. NK activity in cord blood is also depressed com pared to that in adults. Cord blood is a very rich source of hemopoiet ic progenitor eels. The spectrum of progenitors shows a predominance o f early progenitor cells when compared with bone marrow. These cells p rovide an alternative source to adult bone marrow for stem cells to us e for hemopoietic reconstitution and as targets in the treatment of he reditary deficiencies by gene therapy. These features make cord blood a unique research tool to investigate hemopoietic ontogeny and a uniqu e clinical tool for transplantation.