Quantitation of Haemopoietic Cells from Normal and Leukaemic RFM Mice Using an In Vivo Colony Assay

The conventional diffusion chamber (CDC) as described by Benestad (1970) had been modified to assay the colony forming capacity of RFM bone marrow and spleen cells in agar diffusion chambers (ADCs). The colonies are morphologically identical to those formed by the CFUc in agar culture in vitro and have an incidence of approximately 1 in 10(3) normal nucleated bone marrow cells, and 1 in 10(4) nucleated spleen cells. Comparison of the growth of normal bone marrow cells in CDCs and in ADCs suggests that cell proliferation in diffusion chambers may result from the same precursor cell as detected by colony formation in agar culture in vitro. This proposal is supported by the suicide of approximately 46% of the ADC colony precursor cells following incubation with (3)H-labelled thymidine. Colony formation by haemopoietic cells taken from leukaemic mice appears to be due to the proliferation of a remaining normal cell population alone, while the leukaemic cells in the inoculum form a background of uniformly distributed blast cells. In the case of leukaemic cell culture, there are differences in the results from CDCs and ADCs, and data from colonies in leukaemic ADC cultures are similar to those from normal ADC colonies. These comparisons imply that the ADC technique may be used to monitor the functional capacity of normal bone marrow, by its ability to form colonies, during the development of leukaemia. A humoral effect of a leukaemic environment on the growth of normal bone marrow cells in ADCs has also been detected.