(a) Gadolinium chloride (GdCl3) was injected into corpus callosum lesions at the onset of demyelination (0 dpl) prior to the peak in M1 polarization at 3 dpl. (b) Representative images of control or GdCl3-injected lesions at 3 dpl with immunostaining against iNOS (green), Arg-1 (red), and CD68 (white). Scale bar, 25 μm. (c) Numbers of iNOS+ M1, Arg-1+ M2, or unpolarized (iNOS-, Arg-1-) cells per field ± s.e.m. in control and GdCl3-injected lesions at 3 dpl. One way ANOVA and Newman-Keuls post-test, **p<0.01 (n=5 mice, df=29). (d) Density of PCNA+ Nkx2.2+ proliferating OPCs per mm2 in control and GdCl3-injected lesions ± s.e.m. at 3 dpl. P=0.0496, 2-tailed Student’s t-test (n=5 mice, df=8).