Granulocyte progenitors (CFU-D) in neutrophilic leukemoid reaction are hyporesponsive to macrophage-induced inhibition

The responsiveness of marrow granulocyte progenitors (CFU-D) to macrophage-derived stimulatory and inhibitory factors has been studied using diffusion chamber technique in 12 patients with neutrophilic leukemoid reaction (with granulocyte count in the range between 10-40 G/l) and ten healthy subjects. CFU-D from patients with neutrophilic leukemoid reaction (NLR) revealed a normal reactivity to colony-stimulating activity, whereas they were hyporesponsive to macrophage-derived indomethacin-sensitive inhibition. This altered response was correlated both with the concentration of granulocyte progenitors in the S phase and with blood neutrophilic leukocytosis. In patients with higher granulocyte count and increased concentration of CFU-D during active DNA synthesis a more pronounced hyporesponsiveness of granulocyte progenitors to macrophage-induced inhibition has been found.