Induction of colony-stimulating factor and stimulation of stem cell proliferation by injection of muroctasin.

Modulation of myelopoiesis by anomeric mixture of N2-[(N-acetylmuramoyl)-L-alanyl-D-isoglutamyl]-N6-stearoyl-L-lysin e (MDP-Lys(L18), muroctasin), a muramyl dipeptide analog, was investigated in mice. When BDF1 mice were subcutaneously treated with a single dose of 100 micrograms of MDP-Lys(L18), an increase in the number of peripheral blood leukocytes, a rise in the serum levels of colony-stimulating factor (CSF), proliferation of multipotential stem cells in the bone marrow and the spleen, and an expansion of granulocyte-macrophage progenitors in the bone marrow were observed. These findings suggest that the increase in the number of peripheral blood leukocytes in BDF1 mice by MDP-Lys(L18) is due to CSF production and stimulation of stem cell proliferation.