GM-CSF triggers accelerated myelopoiesis during EAE. (A) CD11b⁺CD115⁺Ly-6C⁺ or Ly-6C⁻ blood cells (left) were enumerated 7 days after immunization of C57BL/6 WT and GM-CSF^−/− mice with MOG peptide in CFA. The data are presented as the fold increase in each subset over their frequency in unimmunized counterparts. Frequencies of circulating Ly-6C⁺ and Ly-6C⁻ monocytes did not differ significantly between unimmunized WT and unimmunized GM-CSF^−/− mice. Clinical scores (right) of MOG-immunized WT and GM-CSF^−/− mice. (B) Left: The number of circulating Ly-6C⁺ monocytes/mL of blood in anti–GM-CSF versus control antibody-treated WT mice on day 7 after immunization with MOG peptide. Mean (± SD) of 4 independent experiments; *P < .05 comparing frequency of Ly-6C⁺ monocytes in rat IgG versus αGM-CSF treated mice. Right: Clinical scores of MOG-immunized WT mice treated with either control antibody or anti–GM-CSF across a range of doses. (C) Left: Frequency of Ly6C⁺ blood monocytes on day 8 after active immunization of WT or GM-CSF^−/− mice. Some GM-CSF^−/− mice received 5 μg of recombinant mGM-CSF 8 hours before phlebotomy. Mean (± SD) of 3 independent experiments; *P < .05, **P < .01 by comparison to GM^−/− mice. Right: Clinical scores of MOG-immunized WT and GM-CSF^−/− mice. Some GM-CSF^−/− mice received 5 μg of rmGM-CSF every day from days 0 to 16 after immunization.