A new assay suitable for enumeration of murine progenitors of granulo-monocytes and for rapid automated assessment of granulo-monocyte growth factors.

A simple and reproducible assay is described for enumerating the progenitors of granulocytes (G) and monocytes (M) present in either the bone marrow or spleen of mice. This assay is based upon the plating of different dilutions of test cells in the wells of Terasaki plates. Negative and positive wells for presence of G and M are scored 7 days later. Minimal estimates of GM progenitors frequency are obtained by analysis of the Poisson distribution relationship between the percentage of non-responding microcultures and the numbers of cells plated. This liquid microculture assay offers many advantages: (1) the ability to assay directly in situ at clonal level different enzymatic activities like non-specific esterase; (2) the ability to screen within 3 days the presence of GM growth factors by measuring the [3H]thymidine uptake of proliferating responsive cells.