In vitro growth of granulocytic colonies from circulating cells in human cord blood.

Human umbilical cord blood cells from 26 were formed in these cultures per 2 x newborn infants and peripheral blood cells i0 nucleated cells plated. The peripheral from 18 adults were cultured in vitro by blood cell cultures from adults gave rise to using the agar-gel method of human 0-1 1 colonies, with a mean of 3, per 2 x hemopoietic cell culture. An increased i0 nucleated cells plated. The average concentration of colony-forming cells was number of cells per colony was 1000-1500 seen in the cord blood cultures. Between cells after 14 days of culture, predom17 and 385 colonies, with a mean of 122, inantly granulocytic. A N INCREASED CONCENTRATION of hemopoietic stem cells has been found in the blood of mouse embryos when compared with the concentration after birth. .2 The method used for these experiments has been the spleen colony technique. A similar in vivo technique is not available for human studies, but a method for in vitro growth of human granulocytic progenitor cells has been described recently by Robinson and Pike.3 By this method granulocytic colonies are formed in an agar-medium layer when bone marrow cells are placed upon a feeder layer containing peripheral leukocytes. The identity of the in vitro colony-forming cell is unknown, but similar studies in the murine system indicate that the in vitro colony-forming cell is a primitive member of the granulocytic cell line, a committed stem cell, more mature than the in vivo spleen colony-forming cell which is considered to be the multipotential stem cell.4 It is, however, still a matter of debate whether a difference exists between the in vitro colony-forming cell and the spleen colonyforming cells in the murine system.5 Evidence for in vitro colony-forming cells circulating in peripheral blood from normal adults has been reported, although in a small number compared with human bone marrow cultures.6’7 In this study, the concentration of in vitro colony-forming cells in human umbilical cord blood was investigated and compared with the concentration in peripheral blood from normal human adults.