STUDIES ON COLONY FORMATION IN-VITRO BY MOUSE BONE MARROW CELLS .I. CONTINUOUS CLUSTER FORMATION AND RELATION OF CLUSTERS TO COLONIES

Colony formation in vitro by mouse bone marrow cells following stimulation by human urine was analysed over a 7‐day incubation period. There was a linear increase with time in the number of cell aggregates (clusters) developing in such plates. Early in the incubation period all clusters were granulocytic although later macrophage clusters developed. Although most fully developed colonies were composed of macrophages, mapping and transfer studies showed that at least half of these had initially arisen early in the incubation period as granulocytic clusters. Copyright © 1969 Wiley‐Liss, Inc.