Published online before print February 16, 2007
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* Departments of Neurology and Pathology, University of Southern California Keck School of Medicine, Los Angeles, California, USA; and
Department of Neurosciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
1 Correspondence: Department of Neurology, University of Southern California Keck School of Medicine, MCA 245, 1333 San Pablo Street, Los Angeles, CA 90033, USA. E-mail: vanderve{at}usc.edu
ABSTRACT
Similar to the regulation of vasodilation, the balance between NO and superoxide (O2) regulates expansion of activated T cells in mice. Reduction of suppressive NO levels by O2 is essential for T cell expansion and development of autoimmunity. In mice primed with heat-killed Mycobacterium, a splenocyte population positive for Gr-1 (Ly-6G/C) is the exclusive source of both immunoregulatory free radicals. Distinct Gr-1+ cell subpopulations were separated according to Ly-6G expression. In culture with activated T cells, predominantly monocytic Ly-6G Gr-1+ cells produced T cell-inhibitory NO but no O2. However, mostly granulocytic Ly-6G+ cells produced O2 simultaneously but had no measurable effect on proliferation. Recombination of the two purified Gr-1+ subpopulations restored controlled regulation of T cell proliferation through NO and O2 interaction. Coculture of p47phox/ and inducible NO synthase/ Gr-1+ cells confirmed this intercellular interaction. These data suggest that bacterial products induce development of distinct Gr-1+ myeloid lineages, which upon stimulation by activated T cells, interact via their respective free radical products to modulate T cell expansion.
Key Words: nitric oxide superoxide myeloid suppressor cells granulocytes monocytes
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