Flow cytometric analysis of the effect of interleukin-1 administration on bone marrow populations in mice.

: We have examined the effect of administration of human interleukin-1 (IL-1) beta on bone marrow populations in mice. The bone marrow population was characterized by flow cytometric analysis of cell volume, right angle light scatter, and cell surface markers. The bone marrow population demonstrated significant alterations following the injection of a single dose of IL-1. The earliest response was a loss of granulocytes, which was followed by an expansion of cells in this population. There was also an accumulation of kappa chain positive B cells 24 h following administration. These cells were lost from the marrow over the next 48 h, accompanied by an expansion of precursor cells. The changes in cell populations were not due to contaminating lipopolysaccharide (LPS), although the effects could be mimicked by injection of high doses of LPS. Significant effects could be detected with single dose administration of 10 micrograms to 10 ng of IL-1 per animal. The effects of a single high dose (10 micrograms) were mimicked with multiple injections of low doses (5 x 10 ng), suggesting that the intensity of the response is related to the pharmacokinetics of IL-1. These results indicate a potent effect of IL-1 administration on murine bone marrow granulocyte and B lymphocyte populations. The studies described offer a means for the analysis of the effects of IL-1 in vivo.